Et Tunc Nulla Erat X (Dinos 3)

Et tunc nulla erat X 10
(And Once There Was)
Dinos: Part 3 of 3

The Theropod March to Bird:
In the following theropod groups it becomes increasingly difficult in determining what is deemed a dinosaur or a bird.

Avialae: The other major clade subdivision of eumaniraptorans is, Aviale (A-vee-ale-e) as the sister group of Deinonychosauria. The term is Latin meaning ‘bird wings’ and for sure it represents dinosaurs that took flight leading eventually to birds. With a temporal range from the Late Jurassic to the present 165-0 mya, avialans include all the so-called ‘proto-bird’ ancestral dinosaurs directly linked to birds. As an apomorphy (dependent on physical features) based clad, the general term for Avialae is: all dinosaurs that had feathered wings, which entails long forelimbs and fingers used for flapping flight, along with birds that descended from them.
Artist: Rainbowleo  Avialae
The main characteristics of avialans were first that they are the groups of flying dinosaurs, which of course led to birds. Secondly, avialans were small and lastly, they had features that were inherited way back down the dinosaur lineage in possessing feathers, bipedalism, pneumatized bones, soft tissue air sacs that pumped air into stiffened lungs, triangular skull shapes, the use of gastroliths for digestion, nesting techniques, thermoregulation and the theropod manus (hand) digits (fingers) of I, II and III (1st, 2nd and 3rd fingers). Of course, something as mundane as crouching was inherited by avialans from non-avian dinosaurs, an important contribution to brooding eggs.

Theropodal/Bird crouching
In reference to the above illustration: [A] While standing, or at the midpoint of a step, for balance, forces applied by the feet (red) must match the force of body weight (blue) pointing downwards from the center of mass (yellow/black). [B] When the feet move forward the center of mass moves forward. [C] This forward motion forces the limb to crouch in order to maintain balance.

As a group, avialans shared traits in having elongated digits (fingers), the skeletal muscles became larger due to hypergenesis/hyperplasia (increase in amount of organic tissue with cell proliferation as resultant) in serving against hypothermia in particular in hatchlings and evolved adaptations for flight or swimming due to vestigiality as consequential to bipedalism.         

One interesting note here, some paleontologists like the esteemed, Gregory S. Paul feels dromaeosaurids may have actually devolved from primitive avialans losing the power of flight while keeping their feathers. This is similar to the modern ostrich and other ratites and the time scale fits as primitive avialans came first 22 million year earlier than dromaeosaurids. In fact, there have been dinosaur finds that have been very confusing, like Serikornis or Anchiornis in whether they were dromaeosaurids or avialans.
Artist: Herschel Hoffmeyer  Dakotaraptors battling T. rex
There are many genera under the clade, Avialae with most classified under the sub clades of Avialae. The first subgroup that is the basal most avialan clade leading to birds is in the family, Anchiornithidae (On-chee-or-nith-ah-day) with nine genera.

Euavailae (U-a-vee-ale-e), meaning, ‘true winged birds’ are avialan dinosaurs getting closer on the march to birds. Avebrevicauda (Hav-brev-e-caw-dah), meaning ‘birds with short tails’ in reference to the shortened pygostyle, has no more than ten caudal vertebrae. Pygostylia (Pay-gus-style-e-uh) are avebrevicaudan dinosaurs with short fused caudal vertebrae.
Avebrevicauda Clade
The following are the final avialan sub-clades leading to birds as pygostylians. Ornithothoraces (Or-nith-o-thor-ace-eez) taxa had a temporal range from 130.7-0 mya during the Early Cretaceous down to the present, with the term, Ornithothoraces meaning ‘bird thoraxes’. Enantiornithes (In-an-tie-orn-ah-theez) and Euornithes (U-orn-ah-theez) are the two major subdivisions of Ornithothoraces. Enantiornithes means ‘opposite birds’ while Euornithes means, ‘true birds’ and while both groups became extinct, the euornitheans are the lineage that led to birds. Ornithuromorpha (Or-na-thur-o-morph-ah) has 13 genera and one subclade in Ornithurae (Or-na-thur-ee) which has eight genera. The last in following is the final subclade, Aves (Ah-vez), which of course includes all extinct and extant birds.

There are only three avialan genera and one family that are not in the direct common ancestry to birds. The genera are: Archaeopteryx (R-key-op-teh-rix) from the Late Jurassic 150.8-148.5 mya; Jeholornis (Jeh-o-lor-nis) from the Late Cretaceous 122-120 mya and Rahonavis (Rah-hun-ah-vees) from the Late Cretaceous 70 mya. The family is Anchiornithidae (Ang-key-or-nith-ah-day) from the Late Jurassic to the Early Cretaceous 165-122 mya.
Archaeopteryx fossil
Archaeopteryx is the famed first bird-like dinosaur found in the famous ‘Solnhofen’ limestone of Bavaria that we all know, or do we? Since that first time in 1861there has been seven more fossil findings, but due to some discrete sizes in skeletal structures, like the length of the cauda (tail) and phalanges (fingers), some paleontologists have wanted to describe them as different Archaeopteryx species and make a family out of it, calling it Archaeopterygidae. I won’t go into the specific names because other paleontologists feel all the other fossil remains are still the one and only, A. lithographica and personally, I agree with them. Most likely the skeletal size differences are the result of regional pressures, sub adults versus fully grown adults, ontogenetic development variances, or even dimorphism. But remember, the argument is still contentious and it may well bear out that a family is called for.

Nonetheless that doesn’t take away from the importance of the Archaeopteryx discoveries. It is a transitional form of non-avian maniraptorans and birds, but is more related to maniraptorans, like Dromaeosaurus than it is to birds.

At 50cm/20in long, Archaeopteryx still was fully feathered with the caudal (tail) and wing feathers rounding off at the distal ends. One fossil finding under electron microscopy showed the feathers still retained the pigment, melanin concluding that the feathering was black. Also, in being bird-like, Archaeopteryx’ inner ear was more like modern birds than maniraptoran ears and the brain area dedicated to vision took up 1/3 of brain size. However, unlike birds it still possessed a full set of small but sharp teeth, a long bony caudal (tail), gastralia (belly ribs) and three wing claws functional enough to grasp prey.
Artist: Paul D. Stewart  Archaeopteryx
Archaeopteryx most likely could not sustain powered flight, but it could perform leaping, gliding and possibly even short flights. The wings were small compared to body size and the Archaeopteryx sternum was flat indicating a lack of strong flight muscles in that with modern birds, flight muscles are attached to the sternum. The scleral rings show that Archaeopteryx was diurnal and the rounded tail and wing feathers support it inhabited forested areas as most extant forested birds have rounded feathers. In being cursorial (ground dwelling), it probably also used its hind limb and forelimb claws for scaling the trunk of trees to glide or to roost during nocturnal hours as larger forest birds like wild turkeys and the African chicken fowl do.

With a length of 0.8m/2.6ft, Jeholornis was the largest avialan until the latter half of the Late Cretaceous in which the ornithurine, Hesperornithes reached a length of 1.5m/4.9ft. There are three species in: J. prima, J. palmapenis and J. curvipes. Fossil remains have been found from the Chinese, ‘Jiufotang’ and ‘Yixian’ formations detailing that Jeholornis was an herbivore subsisting primarily on cycad and ginkgo seeds along with small fruits as witnessed in caprolithes (fossilized fruit). With seeds and caprolithes found in the crop, gastroliths were also found in the digestive tract.
Jeholornis fossil

Even though the shoulder blades were more on the sides of the body than on top of the back like birds, the forelimbs were larger than the hind limbs in Jeholornis and were more equipped for powered flight than Archaeopteryx was. The flight feathers were asymmetrical and aerodynamic. With a partially reversed first toe, the claw curvature alludes to the fact that it could perch on limbs. The halluces (singular: hallux ~ innermost digit of vertebrates’ hind foot) were short and along with short hind limbs, it was not a fast runner. The skull and snout were short, but robust, with J. prima lacking teeth in the upper jaw (maxilla) with three small teeth in the mandible (lower jaw), while J. palmapenis had teeth in the middle of the maxilla.

Artist: Aijuan Shi  Jeholornis
The most unique trait of Jeholornis was that it had two tail feathers. The first was at the base of the tail composed of eleven pennaceous feathers forming a frond that could jut at an upright angle and surely must have been used for display as sexual dimorphism in the male. The other tail feathers were located at the end of the caudal tail, were vaned, rounded and used for flight.                

The family, Anchiornithidae had a temporal range of 165-122 mya during the Late Jurassic to Early Cretaceous. Anchiornithids may be the most derived and closest transitional form of avialans to the most basal of birds. Lightly built fully feathered carnivorous/insectivorous avialans, with long legs, arms, fingers and tails, anchiornithids anatomically resembled Archaeopteryx and even the dromaeosaurid, Microraptor, but physically on outside appearances looked like birds. At only 30cm/12in in total length, Eosinopteryx was the smallest avialan, while Pedopenna and Yixianosaurus were both the largest at 1m/3.3ft.
Anchiornithidae Clade
There is a certainty that all anchiornithid species possessed pennaceous feathers, although between genera, there were variances in feathering from being asymmetrical or symmetrical with short downy tail feathering. Even though they were pennaceous, some species lacked barbules that would have given a shaggy appearance. With all this feathering, even those with shorter legs possessed leg feathering where the feathers were pennaceous and covered down past the ankles. The wing feathers were symmetrical and slender making it almost useless for powered flight, but anchiornithids could surely glide.

The distinguishing features were in having ‘fan-shaped’ posterior neural spines; the acromion margin (bony process on the scapula) hooked outwards and the inside surface of the proximal part of the fibula was flat.  Also, the presence of furrows on both sides of the phalanges (fingers) is a feature shared by all anchiornithids.  Sharing a trait with most troodontids, the anterior dentary teeth were numerous and more closely spaced than teeth in the middle of the tooth row. 

Anchiornithidae family members came from what is now the ‘Tiaojishan Formation’ of China and the country, Germany. The family has nine genera, which are: Serikornis (Say-ree-kor-niss) from the Middle-Late Jurassic 165-162 mya; Pedopenna (Puh-dop-in-nuh) from the end of the Middle Jurassic 164 mya; Caihong (K-hawn) from the Late Jurassic 161 mya; Anchiornis (Ang-key-or-niss) from the Late Jurassic 160.89-160.25 mya, of whom the family is named after; Xiaotingia (Zhau-tin-gee-ah) from the Late Jurassic 160 mya; Aurornis (Or-ror-niss) from the Late Jurassic 160 mya; Eosinopteryx (E-oh-sye-nop-ter-ix) from the Late Jurassic 160 mya; Ostromia (Oss-trom-ee-uh) from the Late Jurassic 150.25 mya, in which its Haarlem TM 6428/29 fossil was once considered an Archaeopteryx species and Yixianosaurus (Yee-see-en-o-sawr-us) from the Early Cretaceous 122 mya.
Artist: Emily Willoughby  Serikornis 
Serikornis is the oldest anchiornithid (165-162 mya) and was rather small at 34cm/13.4in. The fossil find is from the volcanic interspersed with sedimentary rock ‘Tiaojishan Formation’ of China. Even though it was covered in multiple types of feathering, the fossil’s skeletal anatomy suggests it was terrestrial and not arboreal. Fossil feather imprints include wispy bundles along the neckline, short and symmetrical vaned feathering along the forelimbs along with fuzz intermingled with long pennaceous feathers on the hind limbs. The tail was covered proximally by filaments and distally (tail-end) by fine retrices.

Serikornis fossil
Unlike coracoid crests found in other anchiornithids as in Anchiornis, Serikornis’ coracoid was devoid of a crest. In the hip, the ilium bone’s postacetabular blade is stout and squared, while the ischium has a narrow and unciform (curved) process. The front four maxillary teeth are twice as long as the other tiny teeth, but all were sharp and cone-shaped. The fossil’s cervical vertebrae have small pneumatic cavities known as camelles system, which is a derived coelurosaurian condition.

Artist: Zhao Chuang  Caihong
At 40cm/16in long, Caihong was small; about the size of a mallard duck. The fossil remains were found by a farmer in China’s Hebei, Province. The full name is, C. juji with the specific name meaning in general Chinese, ‘big crest’. The genus name, Caihong is Mandarin and refers to ‘rainbow’ and for good reason. While sporting a long fan tail, Caihong had a crest of feather colorations about the head, neck and throat that were a rainbow of iridescent colors. The iridescence was much like that of the black feathered Microraptor, mentioned under microraptorines, but Caihong was displaying iridescence some 41 million years earlier.  

The preserved melanosomes’ cell pigments detail splashes of orange, lite green, burnt red and blue around the cranial and neck areas that match the iridescence of hummingbird feathers. Aside from the iridescent feathers, Caihong is also the earliest known not just dinosaur, but animal to support asymmetrical feathering. Although asymmetrical feathering is on modern birds’ wings, they were on Caihong’s tail. Only the body feathering was shaggy and not iridescent.
Caihong feather fossil
Caihong had a small bony crest atop the lacrimal bone of the snout that resembled the protrusive crest of much earlier dinosaurs. Instead of the typical maniraptoran triangular skull, it had a long slender snout. The snout had a troodontid trait in that the strut separating the maxillary fenestra from the antorbital fenestra was pierced by a connecting channel. The spine of Caihong was composed of ten neck vertebrae, thirteen back vertebrae, five sacral vertebrae and twenty-six cauda vertebrae.

Eosinopteryx, is the smallest of anchiornithids, with its fossil remains coming from the western portion of China’s, ‘Tiaojishan Formation’. the remains were well preserved in presenting virtually a wholly articulated skeletal anatomy of a young adult with feather impressions.
Eosinopteryx fossil
With uncurved toe claws, Eosinopteryx was a fast runner and most likely lived in a forest setting in judging from the surrounding plant fauna fossils. Although as straight instead of curved, the claws would not afford tree climbing or predation like curved claws afforded other anchiornithids. With this in mind, it was primarily an insectivore while occasionally running after small vertebrates.

Artist: Emily Willoughby  Eosinopteryx
The snout of Eosinopteryx was blunted and short, even shorter than the diameter of the eye sockets. Compared to most avialans, the tail was very short when contrasted to body size. The primary wing feathers were longer than the humerus (upper arm bone). It had hind wings, but unlike other leg-winged anchiornithids, its lower tarsals and feet were featherless. With complex wing bones, it would not have allowed flight.

Anchiornis fossil
Anchiornis had a length of 40cm/16in and as, Serkornis and Eosinopteryx it also came from China’s ‘Tiaojishan Formation’. Over hundreds of Anchiornis fossils have been discovered with many in impeccable preservation. Embedded in pyroclastic rock layering that can be split, the fossil remains not only show detail in the skeletal anatomy, but also in the feathering and skin. The skeletal structure was very similar to the above mentioned, Eosinopteryx, just a bit larger and also possessed straight claws in the toes.

Anchiornis wing fossil with skin (white)
The long wing (forearm), which measured 80% of the body’s length and manus (hands) were covered in eleven primary and ten secondary feathers with both forming rounded feather wings. There were three phalanges (fingers) with claws ending on each wing, but the longest two fingers were bound together by skin and wing tissue. The very long hind limbs were covered in long vaned feathers that were not structured for flight and were most likely a vestigial trait inherited from anchiornithid ancestry. The toes were layered with small scales. The foot pads, as in birds, were covered in even smaller scales.

Artist: Zhao Chuang  Anchiornis
The feathering impressions of Anchiornis fossils still retained melanosomes; pigment cells that give coloration. Through fluorescence evaluations it was found that the color patterns were gray to grayish black on the body while the wings were white with distal black spangles. The face had rufous red speckles with a rufous red crest starting from the forehead exceeding back to the crown of the neck.           

Xiaotingia as well came from the ‘Tiaojishan Formation’ of China’s, Jianchang County of Liaoning Province. With a length of 0.6m/2ft, it had long and robust forearms, which at first was thought to support powered flight. Due to this thinking, it was proclaimed to be the first bird, trumping Archeopteryx of that crown by 10 million years. But as it stands, both cannot claim the crown, for neither one qualifies to being a bird.
Artists: Xing lida & Liu Yi  Xiaotingia 
The fossil was so well preserved that the body feathering still had its structure. In animals, there are no pigments for blue; plants use anthocyanin to produce blue pigments. Most current mammals only produce melanin in various forms such as eumelanin and pheomelanin that can produce a wide range of colors except for blue and green shades. Extant birds like, flamingoes and cardinals reach their colors through their diet metabolizing the particular food’s pigment once it reaches the follicles of their feathers. But most extant animals that are blue or green produce the coloration through a specific structure that absorbs the whole spectrum of light, except for wavelengths of blue or green that it reflects back out to an observer to see. That’s why Opheodrys (the N. American smooth and rough green snakes) appear green and why the blue jay is blue. The specific structure of their scales and feathers reflect the green and blue wavelengths by scale or feather cells dying leaving stringy molecules of keratin interspersed with air pockets that reflect and scatter the green or blue wavelengths.

Xiaotingia fossil
Now back to Xiaotingia’s fossil. The body feathers’ specific structure was so well preserved that it reflected blue. Morphologically, Xiaotingia was very similar to Archeopteryx, but Archeopteryx was a meat eater and Xiaotingia with bulbous teeth was more of a plant eater or of shellfish or, both. We don’t know if Xiaotingia’s diet gave its blue hue, but the feather structures indicate that it did and still does in the remains.

Euavialae and Avebrevicauda are two avialan subclades that led to Pygostylia. I won’t go much into detail with these two as they are simply a sequential line to pygostylians. All three have a temporal range of 131-0 mya with a chronological order in phylogenetically putting the most primitive first, which would be: euavialans =› avebrevicaudans =› pygostylians.

Euavialae literally means, ‘true winged birds’ and is the major separation between feathered dinosaurs and modern birds. Besides in the clade Euavialae leading to birds through Avebrevicauda, it holds one genus that was monotypic as a euavialan in Jixiangornis. Many scientists call euavialans ‘primitive birds’, but as a scientist and junior paleontologist myself, I’m still going to refer to them as dinosaurs. Under ‘Birds’ I’ll give the true definition of birds with a list of anatomical traits.
Artist: Jack Wood  Jixiangornis
In having a temporal range of 124.5 mya during the Early Cretaceous, Jixiangornis (Jix-sang-or-nees) was a primitive euavialan and through the current fossil record was no predecessor to future lineages. The fossil remains came from the ‘Yixian Formation near China’s Beipiao City of western Liaoning, Province.
Jixiangornis fossil
At 0.8m/2.6ft long, Jixiangornis, with long forelimbs (forelimbs were over 130% longer than hind limbs) indicating its forceful aerial flight was capable of stronger flight than that of Archaeopteryx. Even though it was toothless like birds, but unlike more derived avialans still retaining teeth, it coevolved a toothless snout independently of birds. Unlike the more advanced pygostylians and birds with short tails, it still possessed a long tail having 27 caudal vertebrae. The sternum was large, but the keel was weak.

Avebrevicauda Clade

Avebrevicauda literally means, ‘birds with short tails’ and so named to separate dinosaurs from their reptilian long tailed ancestors to those with ten or fewer free caudal (tail) vertebrae. Considered a stem based clade, Avebrevicauda contains all known avialans that had lost the hyperextended pedal/pes (foot/feet) digit II (second toe). This is a form of ‘oligodactyly’ when a digit from a limb never develops and is much more common than ‘polydactyly’ when an extra digit (toe or finger) is developed. Both anomalies are caused from genetically or familial altercations in the fetal stage. The Avebrevicauda clade includes the family, Omnivoropterygidae (Alm-nih-vor-op-teh-ridge-ah-day) and the whole of Pygostylia descendants, that includes the clade node order, Confuciusornithiformes (Cun-fusch-suh-sor-ah-nith-e-for-meez) and its family and the node based clade, Ornithothoraces along with its subdivisions.

Omnivoropterygidae: With a temporal range of 125-120 mya during the Early Cretaceous, omnivoropterygids were primitive avebrevicaudans and most likely were a short and regional occurrence with all coming from a 120 million year old section of the ‘Jiufotang Formation’ of Chaoyang, China. Because there are only teeth in the upper premaxillaries, omnivoropterygids are considered omnivores, hence the name. There are two omnivoropterygid genera with one species in each and they are: Omnivoropteryx (Alm-nee-vor-op-teh-rix) and Sapeornis (Sape-or-niss). There is an order above Omnivoropterygidae, but there are no members outside of the family Omnivoropterygidae; its name is, Omnivoropterygiformes. Also, due to some similarities, although there are some primitive differences with Omnivoropteryx to oviraptorosaurs, those similarities may make Omnivoropteryx a junior synonym of Sapeornis and the name may be abandoned which would also replace the family name of Omnivoropterygidae to Sapeornithidae. Just keep that in mind for future referencing. Whew…a lot of Omni’s in there.
Artist: Yike Xu  Sapeornis
Having a temporal range of 124.5-120 mya during the Early Cretaceous, Sapeornis was a larger avialan reaching a length of 33cm/1.1ft. The manus (hands) possessed three fingers on each forelimb with the outer two fingers having two phalanges and the middle with three. The skull only possessed a few teeth in front on the upper premaxillaries. The forelimbs were one and a half times longer than the hind limbs giving a large wingspan, but the shoulder girdle structuring was ill adapted to flapping. As far as primitive traits go, the long tail bone was absent while gastralia were bones present supporting the abdomen.

Sapeornis fossil
With Sapeornis fossils coming from the ‘Jiufotang’ and ‘Yixian’ formations in the western half of Liaoning, China, it probably was an open country animal with the capability to perch and glide or soar seeking out feeding grounds, as the gastroliths found in the fossil remains indicate a harder source of diet such as seeds.

Pygostylia: Pygostylians occurred, 131-0 mya from the Early Cretaceous to Present. Pygostylian features closed the gap in what is a dinosaur and what is a bird. In fact, many esteemed paleontologists indeed do refer to them as primitive birds. However in my perspective, perhaps proto-birds, but not birds, at least not in saying they possess all the same characteristics as Neornithes (modern birds).
Bird anatomy with pygostyle
Pygostylians are named for the pygostyle, a triangular plate shaped distal bone tip of tails formed from the fusion of the shortened caudal vertebrae supporting the tail feathers and the muscles controlling the feathers. The intention is to separate out all avialans with short stubby tails from the more reptilian avialan tails. The more primitive Pygostylians had longer rod-shaped pygostyles while the more derived from Ornithothoraces onwards into birds, had a plowshare-shaped pygostyle.

Aside from the pygostyle, there’s considered three other main features of pygostylians and they are: the total absence of an accessory joint found in most archosauromorphs known as the ‘hyposphene-hypantrum’, a reversed pubic bone and a bulbous medial condyle (round prominence at the end of a bone) of the lower leg bone known as the tibiotarsus.
Pygostylia Cladogram
The clade, Pygostylia is divided into the order, Confuciusornithformes; the family under it, Confuciusornithidae and Ornithothoraces along with its family members.

Confuciusornithiformes (Cun-few-shus-or-nith-e-for-meez) contains members that first evolved the bird-like beak occurring 131-120 mya in the Early Cretaceous. Also, according to the fossil record, it appears that confuciusornithiforms are the first to evolve vitellogenesis, commonly called, ‘yolk deposition’ where nutrients being deposited in the oocyte, or female germ cell involved in reproduction of lecithotrophic (oviparous animals that lay eggs with little or no other embryonic development within the mother) organisms.

All known confuciusornithiform fossils lacked teeth in having a beak instead of a snout, but this was independent of birds. The beak tip ended in a point. Generally, they were very small but with robust forelimbs supporting long and narrow pennaceous feathers.

The order, Confuciusornithiformes is divided into the family, Confuciusornithidae (Cun-few-shus-or-nith-ah-day) and the most primitive confuciusornithiform, in the monotypic genus, Eoconfuciusornis (E-oh-cun-few-shus-or-nees).
Artist: Nobu Tamura  Eoconfuciusornis
Eoconfuciusornis is a primitive confuciusornithiform and not a confuciusornithid, but is sister to the family. Occurring 131 mya during the Early Cretaceous, the fossil remains were found in the ‘Sichakou Beds’ of the ‘Dabeigou formation’ near Fengning, China. The remains show it had a length of 47cm/18.5in and are of a relatively complete but compressed skeleton and well conserved actual feathering.

Eoconfuciusornis fossil
Researchers used both scanning and transmission electron microscopy to gather microscopic details of Eoconfuciusornis’ feather surfaces and their internal structure. The scientists had two goals; to see if the feather filaments were made up internally of keratin and to learn if it was microbody contaminants like bacteria that were giving the feathers its colors instead of melanosomes. What they found was that indeed the feathering was composed of keratin, like in modern birds and it was melanosomes coloring the feathers and not bacteria. They also discovered that the beak was entirely made up of keratin instead of bone just like in modern birds.

Artist: Jaime Chirinos  Confuciusornis feducciai
Confuciusornithidae: Members had a temporal range of 131-120 mya during the Early Cretaceous, which contains two valid genera in: Confuciusornis (Cun-few-shus-or-nees) and the holotypic genus, Changchengornis (Chan-jing-or-nees). There is another genus in Jinzhournis, but is considered dubious and a junior synonym with the remains most likely belonging to Confuciusornis. About the size of a pigeon, all three Confuciusornis species had a length of ~ 50.8cm/20in with a wingspan of 0.7m/2.3ft.

For the genus, Confuciusornis there are currently three confirmed species and they are: C. sanctus (sanque-tuce), C. dui (d-u-i) and C. feducciai (feh-dook-say). Confuciusornis species lived 125-120 mya ago during the Early Cretaceous.  There have been hundreds of well preserved and articulated fossils found in the ‘Yixian and Jiufotang’ formations of China. In fact, on a 100 meter squared area forty fossils were found in articulated condition. This was a result of volcanism as all the fossils were found in tuff sediment, which is the result of compacted volcanic ash.
Confuciusornis morphology
The skull held a pointed toothless beak and closed orbitals (eye sockets); however, there were jaw bone grooves that were vestigial remnants of tooth sockets. As far as the closed eye sockets, they were closed due to the presence of a triradiate postorbital separating the eye-socket from the lower temporal opening. Also, the nasals were forced to the sides of the beak due to the beak’s premaxillae stretched out into the frontals (forehead).

Confuciusornis fossil toe scales
Although Confuciusornis species had a pygostyle, there were no tail flight feathers, but in displaying sexual dimorphism, the male had two extended, ribbon-like feathers that did not have a keratinous continuous spine running the full length of the feathers; rather, there were two smaller central spines with one positioned at the base and the other at the distal end of the feather. Due to exceptional fossilization, the feathering was analyzed through electron microscopy for melanosomes.
With robust beaks, the Confuciusornis diet most likely was predominately omnivorous and insectivorous, but in a fossil where the crop would have been was a compacted wad of Jinanicthyes’ (a small extinct fish) skeletal remains. So, it may have been piscivorous as well.

Cofuciusornis wingbone
There are transitional traits in Confuciusornis where it is more basal but yet more derived. Possessing three claws on each manus (hand) with digit I claw being the largest while independent to the rest of the hands movement and a basal skull made it more primitive. On the other hand, having a bony sternum and a pygostyle in place of a long caudal tail made it more derived. What were distinct characteristics were in the forelimbs with a foramen (bone opening) in the deltopectoral crest (longitudinal ridge along the humerus) along with the proximal (humerus) fusing with metacarpals’ (set of bones between wrist and finger bones) digits II and III (second and third fingers) to the carpometacarpus (fusion of the carpal and metacarpal bone making a single fused bone between the wrist and the knuckles).

As far as flying is concerned, Confuciusornis could fly; how well is still up for debate. The unusually long forelimbs supported primary asymmetrical flight feathers, its fused wrists and ossified sternum with a central keel, possessing strut-like coracoid bones which could form a solid base for wing muscle attachments and its deltopectoral crest which provides powerful upstrokes all point to the fact it could fly. However, it lacked an aula (an extension process formed by feathers anchored to the first digit of the hand as in modern birds), the forearms lacked any quill knobs and the heavily-built and immobile skull was incapable of the kinesis of modern birds in the ability to raise the snout relative to the back of the skull.
1st: Franz Anthony C. sanctus 2nd: Daniel Bensen C. dui   
Through electron microscopy analyses, melanosome (organelles containing colors) evaluations showed that C. sanctus had hues of gray, black and reddish browns, while the male ribbon tail feathers would have been totally black and the wings black with a white row through it. Through laser fluorescence, details in soft tissue were observed such as the patagium, which was larger than in modern bird winged patagiums, the tiny reticulate scales of the toes and foot soles along with fleshy sole pads supported by the phalanges and metatarsals. The sole and toe scales along with a reversed digit I (first toe) and toe padding gave stability in perching.
Artist: Matthew Martyniuk  Changchengornis
Changchengornis lived 124.6 mya during the Early Cretaceous although closely related to Confuciusornis, it was much smaller at 20cm/8in long. It is a holotype with the fossil remains coming from the ‘Chaomidianzi Formation’, known previously as the lower section of the ‘Yixian Formation’ of china was very much like the Confuciusornis species in physiology and anatomical traits. As in Confuciusornis, the male had the two ribbon-like tail feathers, the foot structure was adapted for perching; it possessed the same three fingered claws and the beak was toothless and both had a long pygostyle.
Changchengornis fossil
The unique traits in Changchengornis was more in the skull region where the slightly hooked beak was more pointed and at the top of the cranium was a head crest, but also the deltopectoral crest (a bone ridge near anterior end of the proximal humerus) was not pierced as in Confuciusornis. With the difference in the beak form, there is debate on whether it was an omnivore, insectivore, insectivore or even a piscivore.                         

Ornithothoraces ~ One way to look at Ornithothoraces (Or-nith-o-thor-ace-eez) is that when it comes to evolution, this group is kind of like the halfway house between dinosaurs and birds. Technically, this means nothing but perception and perception is not always reality, for a ‘halfway’ perceived evolved species leads to teleology as if one particular taxon group is ‘predestined’ to evolve into another taxon. This halfway house rule of thumb is not scientific in application, however, in turning the page towards descending speciation it does give the layman, as myself, a clearer picture of relationships.
Ornithothoraces Cladogram
The Ornithothoraces clade has a temporal range of 131-0 mya years ago from the Early Cretaceous to Present. The range may be pushed farther back, as the enantiornithean, Noguerornis comes from not yet conclusive rock strata age tentatively dated at 145.5mya. As mentioned earlier, Ornithothoraces is divided into two major subdivisions composed of enantiornitheans and euornitheans. These two divisions separate out the line that dead ended (Enantiornithes) and the line (Euronithes) that became extinct but led to birds. The common ancestor to both these groups making up Ornithothoraces is the enantiornithean, Sinornis.     

Ornithothoracines’ skeletal anatomy included a keeled sternum (breastbone), elongated coracoids (hook-like structures on lateral edge of scapula), the shoulder’s glenoid joint and semi-rigid ribcage had been modified from earlier avialans. Also, there was an absence of gastralia (Singular: gastralium dermal bones found in ventral body wall of reptiles), the scapula terminated distally into a sharp point and the pygostyle, although primitive, fused the most distal caudals into a short tail.

In various literature and even a few early periodicals, you might come across the name, enantiornithean as, ‘enantiornithine’ and that also goes for euornithean as, ‘euornithine’. This infers that they are subfamilies but they are not. So, the ‘ine’ suffix is wrong. 
Enantiornithes (E-nan-tee-or-nah-theez) ~ Enantiornitheans are the most speciose avialans of the Mesozoic found around the globe, except Antarctica and were widespread in the Early Cretaceous Asia and Europe coexisting with relatively modern birds for nearly 24 million years until the Cretaceous/Paleogene Extinction. All of them possessed teeth and clawed fingers and besides the teeth and claws, the main difference between enantiornitheans and birds was in the articulation between the scapula and coracoid. This entails the shoulder bones where the concave/convex socket joint involving the scapula and coracoid in enantiornitheans operated exactly the opposite or in reverse as do modern birds.

Evidence shows that there wasn’t much parental care concerning enantiornitheans, much unlike modern birds’ devoted parental care. With enantiornithean hatchlings hatching from eggs laid on the ground, they would soon have to scamper up trees before being eaten by other animals. Within a week they had feathers and we know this from observing the many hatchlings that were encased in tree sap that fossilized into amber. These amber fossil finds show exquisite detail of feathers, skin and scale features such as morphologies and coloration.
Enanriornithean chick encased in amber
There are multitudes of enantiornitheans, so we’ll break them down by the cladistic families. There are five families of enantiornitheans and they are: Pengornithidae (Pen-go-r-nith-ah-day) from 130.7-120 mya during the Early Cretaceous; Bohaiornithidae (Bo-ha-e-or-nith-ah-day) and Longipterygidae (Lon-gip-ter-ige-ah-day) both from 125-120 mya; Avisauridae (A-vah-sawr-ah-day) from 125-66 mya during the Early to Late Cretaceous and Gobiopterygidae (Go-bee-op-ter-ige-ah-day) from 122-120 mya during the Early Cretaceous.

Before getting into enantiornithes families, first off we’ll touch base on the holotypic basal enantiornitheans. There are at least 52 species of enantiornitheans, but we’ll start with nine holotypic genera in: Protopteryx (Pro-top-tuh-rix) from the Early Creataceous 131 mya;  Iberomesornis (I-beh-roe-matsor-neez) and Eoalulavis (E-o-ah-lu-lay-viss) both from the Early Cretaceous125 mya; Liaoningornis (Leh-ow-ning-or-neez) and Eoenantiornis (E-o-en-an-tee-or-neez) both from the Early Cretaceous 124.6 mya;  Sinornis (Sign-or-neez), Cathayornis (Kuh-they-or-neez), Eocathayornis (E-o-kuh-they-or-neez) with all three from the Early Cretaceous 120 mya and Flexomornis (Flex-o-mor-neez) from the Late Cretaceous 96 mya. Even though Cathayornis and Eocathayornis have similar names, they are only similarly related. Sometimes these holotypes are grouped into a clade as, Euenantiornithes.
Artist: Goombasaurusrex  Protopteryx
With conical and unserrated front teeth extending almost midway into the middle of both the upper and lower jaws, Protopteryx is the most primitive of enantiornitheans. Found in the ‘Huajiying Formation’ of Hebei Province in northern China, it was small at only 10cm/4in. Diet is uncertain but most likely was an insectivore of very small invertebrates.
Protopteryx fossil
With the anatomy in the fossil remains showing it was built for flight, it was a forest dweller according to the flora the fossil was found in. However this is a bit of a conundrum, for to maneuver amongst trees in flight, it had to be an acrobatic aerialist. In order to really achieve this it needs a tail to act as a rudder. It had two extended ribbon-like feathers that were primitive. The two tail feathers weren’t capable of assisting in flight as at the base the two tail feathers were needle-like thin while distally only had barbs at the tips. The main feature of the tail feathers were that they were scaly, so they were used either for display, or sensory perception, but not for flight.

A. Protopteryx  B. Eoenantiornis
However, the short wings covered in asymmetrical pennaceous flight feathers, for such a small enantiornithean, it quite possibly could have been acrobatic enough to fly amongst trees. The body was covered in down feathering in which the barbs were laminar instead of hair-like as in true birds. Protopteryx also possessed a procoracoid (an anterior extension of the coracoid bone), a carina (a ridge of cartilage in trachea occurring at the division between the two bronchi) of the sternum, an external tuberosity humerus and deltoid crest; all of which are found in modern birds. Protopteryx was very small at ~ 12cm/4.7in long.

Sculptors: José Manuel & Benito Álvarez  Iberomesornis 
Iberomesornis fossil remains were discovered in Spain’s Early Cretaceous, La Huérguina Formation. Due to bacterial metabolism of the iron carbonate deposits in the formation, the remains were exceptionally preserved, even preserving soft tissue in other dinosaurs like Pelecanimimus.

It was small, around the size of a house sparrow with a length of ~16cm/6.3in. With short wings and a wingspan, Iberomesornis possessed a claw on each wing. Equipped with superb flight agilities and perching ability in utilizing curved toe claws, it most likely caught small insects on the wing to swallow in flight and/or small ground invertebrates to eat while perched.
Sculptor: Jose Salas  Eoalulavis
Eoalulavis fossil remains also came from Spain preserved in the Konservat-Lagerstätten deposits. Due to an anoxic environment, these deposits also exhibit exceptional fossil preservations even of small soft bodied invertebrates. Found sandwiched between two limonite layers, the fossil remains of Eoalulavis also consist of primary and secondary feathers along with some body tissue. The fossil also reveals a ‘bastard wing’ otherwise known as the alula, which is a small feathered projection on the anterior edge of the digit I wing joint and as in modern birds, is used for flying at slow speed and landing.

Artist: Jack Wood  Lianoningornis
Lianoningornis, meaning, ‘bird of Liaoning’ was a small enantiornithean at ~ 10cm/4in. With the sternum (breastbone) deeply keeled allowing for the attachment of stronger and more well-developed pectoral muscles, it was an advanced enantiornithean. With its shoulders situated for a high degree of motion, it was one of the best flyers of its time. This theropod was capable of strong flapping flight and maneuverability in and between trees. The metatarsals (foot bones) were fused distally and proximally, but not lengthwise up or down the foot.

Artist: Jack Wood  Eoenantiornis
At 10cm/4in, Eoenantiornis was small minus the tail which was only 1cm/0.4in long. The wings were short with long claws extending from the three fingers. With a short blunt snout. The wings show that it was readily capable of flight, but was not acrobatically inclined; instead was more of a straight flyer getting from point A to Point B. Landings may have also been a bit clumsy necessitating the gripping of tree bark with the forelimb and hind limb claws, then climbing to a preferable perch. The eye sockets were large and the small toothed snout was blunt.

Eoenantiornis fossil
The environmental flora of Eoenantiornis ’ home range and time span consisted of forests of gingko and conifers inner dispersed with meadows, lakes and streams.  At home on the ground as much as in trees, this enantiornithine most likely was an omnivore with a diet of insects and seeds.

Artist: Danneart  Sinornis
Sinornis quite literally was a dinosaur on the inside concealed as a bird on the outside. Like Archaeopteryx when compared to the body it had a proportionally short toothed snout and in the forelimbs the manus (hands) and carpi were separate. Also of the manus, the metacarpals articulated freely with the distal end of the phalanges (fingers) supporting claws. The pelvic girdle was free and not ossified as in true birds. Further, the pelvis’ lilac blades were erect with the ischium blade-shaped instead of the bird’s strap-shape. Analogous not only with Archeopteryx, but with older theropods the pubis directed ventrally terminating distally into a hook.
Sinornis fossil
But, on exterior appearance, Sinornis was transitional from primitive Archaeopteryx wings to true birds in having advanced avian characteristics. With modified wrist bones it could fold and tuck the pennaceous feathered wings close to the body during flight posing much like a speeding bullet or at rest to entrap body warmth. Breast bone and shoulder structures served as anchors for aerobic flight muscles. With a reversed toe, it was capable of perching, but with the forelimb claws it also could climb. Primarily, it was an insectivore, catching small insects on the wing, in trees or on the ground.

Artist: Leau Bellon  Cathayornis
At 16cm/6.3in in total length, Sinornis was once thought to be synonymous to Cathayornis, but after further study, it was found that indeed they were two separate species with differences in wing digits and claws, the pelvis and pygostyle. As well, Cathayornis was larger in adult size.

Artist: Scott Reid  Eocathayornis
Eocathayornis was found in the ‘Jiufotang Formation’ of northeast China and had a body length of 13cm/5.1in. The fossil remains are of 3-D impressions sandwiched between two slabs and is not a mold or cast of permineralization. Still, there is a lot of detail.

Eocathayornis skull traits show the premaxilla had a long slender nasal process. There were four pointed small teeth anchored in the premaxilla. Each tooth had a constriction at the crown’s base, which is typical of all toothed enantiornitheans. As in Archaeopteryx and Cathayornis, the cranial tip of the premaxilla is hooked and edentulous (toothless). The maxilla’s pointed dorsal process was caudally inclined.

Claws were present on the three digits (fingers). The relatively short sternum had a pair of long caudo-lateral processes and a low and caudally distributed keel. Even though this was a primitive enantiornithean, traits of the scapula were advanced and along with the forelimb and feathering wing structure, Eocathayornis was quite capable of powerful flapping for flight.
Artist: Jack Wood  Flexomornis
Flexomornis is one of the few enantiornitheans that lived outside of Asia, as its fossil remains were found in Texas, USA. Living during the ending of the Late Cretaceous 96 mya, it is one of the more derived basal enantiornitheans linking the Asian ancestral origins. It lived along an ancient shallow sea shoreline in what is now an ancient riverbed near Lake Grapevine and most likely fed on small marine vertebrates and invertebrates. It would have also been a scavenger scouring the coastal shorelines for carcasses.

The name, Flexomornis is in reference to its unique flexed shoulders. In all appearances it looked like a modern bird, but still retained teeth, forelimb distal phalanges (fingers) and claws. As evidenced by the diagnostic scapula, it had a slight variance in muscle attachments than the older enantiornitheans. This would infer that it was a large enantiornithean at ~ 33cm/13in from head to tail tip.
Artist:Jack Wood  Gobipteryx
For the genus, Gobipteryx researchers are in the process of assigning it to its own family as, Gobipterygidae and even its own order as, Gobipterygiformes; this, even though there is only one species in, Gobipteryx minuta. Apparently researchers feel that closely related gobipterygid forms will be discovered later on.

Around the size of a current partridge at 30-33cm/11.8-13in, Gobipteryx, which occurred 72 mya, had a toothless beak formed by the fusion of premaxillae bones. The scapula was long and was well suited to anchoring flight muscles. In addition, the scapula contained a prominent glenoid labrum (a fibrocartilaginous structure that rims the cavity of the shoulder blade) that tapered backwards ending in thin rods.
Gobipteryx fossilized eggs
With fossils found in the Gobi Desert of Mongolia, Gobipteryx cracked eggs and fully developed embryos were found. These fossils provide evidence that Gobipteryx hatchlings possessed superprecocial development in that they were capable of flight immediately upon hatching.           

Pengornithidae: Pengornithids come from China’s, ‘Huajiying Formation’ and the ‘Jiufotang Formation’. These were one of the most primitive groups of enantiornitheans with numerous mandibular (lower jaw) small teeth and on the other end possessed stout legs. With a temporal range in the Early Cretaceous of 130.7 mya, all pengornithid fossil species have come from the ‘Huajiying’ and ‘Jiufotang’ formations of China’s Liaoning and Hebei provinces.

Along with a shortened tail ending in a rounded pygostyle, pengornithids’ main skeletal feature was a hooked outgrowth of the shoulder blade. Most all, enantiornitheans had four long backward projections coming from their breastbones; pengornithids only had two. Pengornithids retained some primitive traits in an elongated fibula and retaining metatarsal V (5th toe).

Pengornithids had the ability to fly, but the feature noted best by them is their capability to vertically climb. Stiff tail feathers, as in woodpeckers were present acting as a prop while the feet were adapted to hold onto branches with the claws well enforced to anchor into bark. With these features pengornithids were predominately insectivores after insects, grubs and other invertebrates hidden amongst the bark; although, Eopengornis is suspected of also being more of a ground dwelling carnivore, due to its recurved teeth. Most were also aerobatic flyers as evidenced in the short fan tail of the Chiappeavis fossil.

Pengornithidae: this is the most basal family of enantiornitheans consisting of four genera; they are: Eopengornis (E-o-pen-gor-neez) from 130 mya in the Early Cretaceous; Pengornis (Pen-gor-niss), Parapengornis (Par-ah-pen-gor-neez) and Chiappeavis (Chi-ap-pay-viss) all three from 120 mya in the Early Cretaceous.

Artist: Jack Wood  Parapengornis
Parapengornis at ~ 28cm/11in in length it was not just the largest pengornithid, but was also the largest of enantiornitheans. Its tail vertebrae were fused and easily could have been used as a prop in climbing trees while searching for insects and grubs. The teeth were sharp and slightly recurved excellent for grabbing and peeling away bark then seizing an invertebrate hiding underneath. The claws on the forelimbs and hind limbs were ideal for clinging to trees. It also had two ribbon-like feathers extending past the pygostyle like the more primitive holotype enantiornitheans. These traits lend evidence to evolving into diverse ecological niches and the qualitative amount of locomotive methods among enantiornitheans.

Parapengornis fossil
Of course Parapengornis is inferred to have lead an arboreal life by the anisodactyl foot morphology with the reversed first digit, but in addition, the metatarsal of digit I (first toe) is more than 30% longer than pes digit II’s (2nd toe) digit III’s (3rd toe) metatarsal. In the pelvic region, the craniodorsal (direction inferring towards the head and back) ramus (branch of bone) is very long in approaching the length of the ventral ramus. The cranial four cervical (neck) vertebrae are short and could not have been used to hammer trees like woodpeckers do.

Until the discovery of Parapengornis with published results in June, 2015, Pengornis was the largest enantiornithean at 25cm/9.8in. But only for a brief few months as its results were published through the internet in January, 2015. Pengornis fossil remains come from the ‘Jiufotang Formation’ of Dapingfang, Liaoning province, China.
Artist: Jack Wood  Pengornis
Pengornis shared a few skeletal traits with the more advanced ornithurines, which were: a globular humeral head that projects further proximally than the deltopectoral crest, a hooked acromion (plural: acromia), which is a bony process on the scapula (shoulder blade) and heterocoelous (vertebrae having saddle-shaped articular surfaces) cervical vertebrae. Whether this is a form of convergent evolution or genetic inheritance is still being debated.

Pengornis fossil
Some morphological features of Pengornis’ skull were: premaxillae were entirely unfused and the 13 small dentary teeth were brachyodont (short crowned teeth as in mammals) and unrecurved; the premaxillary process tapers rostrally to articulate with the premaxilla and the maxilla formed ~ ½ half of the facial margin on each side. Also, for the backbone, the cranial cervical centra were heterocoelous (vertebrae having saddle-shaped articular surfaces), while the caudal vertebrae were amphicoelous (vertebrae concave at the anterior and posterior ends). With the teeth type, Pengornis may have predominately feasted on a diet of hardened exoskeleton arthropods such as beetles and spiders.

Bohairnithidae Clade
Bohaiornithidae: Fossil specimens all come from the ‘Yixian’ and ‘Jiufotang’ of China. Eoenantiornithes is the monotypic sister to bohaiornithids. As in most enantiornitheans, bohaiornithids did not have a toothless beak as birds, but a snout with teeth. However, the teeth varied from other enantiornitheans in being larger, more robust and more conical, but with only the occlusal end (tip of the tooth) recurving instead of the whole tooth curving backwards. The teeth are indicative of a possible durophagus diet of hard shelled creatures, like molluscs, but due to size, with no bohaiornithid any larger than a medium-sized pigeon, it is highly unlikely they were taking on shellfish. Perhaps there were other much smaller hard shelled arthropods they were feasting on like small crustaceans or larger crabs molting.  

Bohaiornithids possessed long and thin lateral trabeculae (bony projections on posterior end of sternum) that extended backwards and outwards. The scapulae (shoulder blades) slightly curved downwards creating a convex top edge and lower concave edge. Digit II, the second innermost toe of the pes (feet) were the thickest, while digit III as the middle toe was the longest. Male bohaiornithids also possessed the two tail ribbon feathers that were iridescent in life.

There are currently eight known genera of bohaiornithids that all came from Early Cretaceous China and they were: Zhouornis (Zow-or-neez) from ~125.4-120 mya during the Early Cretaceous; Sulcavis (Sul-cay-viss) from 125-121 mya during the Early Cretaceous; Shenqiornis (Shen-key-or-neez) from 122 mya during the Early Cretaceous; Longusunguis (Lon-gus-un-giss) and Parabohaiornis (Par-ah-bow-hay-or-neez) both from 120.3 mya during the Early Cretaceous and Bohaiornis (Bow-hay-or-neez), Fortungauvis (For-toon-gau-viss) and Linyiornis (Lin-yee-or-neez) with all three from ~ 120 mya during the Early Cretaceous.      

Artist: Stephanie Abramowicz  Sulcavis
Sulcavis fossil remains from the Liaoning Province of China exemplifies the diversity of teeth forms in enantiornitheans in bearing ornamented tooth enamel and is another enantiornithean with teeth that would aid a diet in consuming hard food such as insects, small fish and even shellfish. The dental ornamentation were grooves on the inside surface of the robust tooth. The teeth were tough, not for tearing flesh or chewing, but for snatching then crunching exoskeletons and afterwards swallowing whole.

Sulcavis fossil skull
At ~ 25.5cm/10in long, Sulcavis was an accomplished flyer even though it had no sternum. With no sternum, the gastralia (dermal bones found in the ventral body wall) ran right up to the coracoids (paired ventral bones of the pectoral girdle). However, with no true sternum, Sulcavis demonstrates how the sternum evolved for flight by enlarging and fusing the gastralia. It still had two claws on each extended forelimb while supporting the wings.

Other anatomical characteristics of Sulcavis were: the skull was longer than the cervicals; the posterior portion of mandible was set deeper than anterior end; posterior portion of quadrate (squarish bone which articulates the jaws) was straight; the retroarticular (cartilage bone that forms at the posteroventral tip of Meckel’s cartilage where the interoperculomandibular ligament attaches) directionally descends and pes metatarsals (foot bones) II and III aligned with I.

Artist: Jack Wood  ♂ Bohaiornis
An adult Bohaiornis fossil found in the ‘Jiufotang Formation’ is also from the Liaoning Province of China. It was a male showing sexual dimorphism with the two ribbon-like tail feathers. With the presence of gastroliths in the thoracic region concerning Bohaiornis fossil finds and in conjunction with the dental morphology and claws alludes to the fact that it led a raptorial life in that it was equipped for grasping and seizing prey. This is a rare trait not just for enantiornitheans, but for avialans as well. The gastroliths found in Bohaiornis are a different occurrence than that found in herbivorous/insectivorous enantiornitheans in shape, number and color. Raptorial birds of today consume generally a few rounded stones, which is consistent with the Bohaiornis gastrolith fossil finds.

At ~ 47cm/18.5in, Bohaiornis was one of the largest bohaiornithids. Its dentary (upper jaw bone) was straight and half the length of the mandible (lower jawbone). Another couple of unique traits were that the sternum was markedly wider than long while the acrimon (process on the outer end of the scapula extending over the shoulder joint) is very robust. The nasal cavities were also very broad.
Artist: Eloy Manzanero  ♀ Bohaiornis

One fossil specimen had small rounded pebbles in its thoracic region. Along with its cranial and dental morphology, and the number and distribution of teeth, Bohaiornis most likely lived a raptorial ecology feeding on small vertebrates and large arthropods like spiders and insects.             

Longipterygidae: With a 125-110 mya span of known longipterygid species, they’ve only been found in the ‘Jiufotang’ and ‘Yixian’ formations of China. Where pygostyles are usually a series of short fused vertebrae, longipterygids had an unusually long pygostyle.

Making up over 60% of the skull, the snout was extremely long with the tip of the snout supporting teeth in the premaxilla (upper front jaw) and rostral portion of the dentary (lower jaw). The shape of the snout was straight, but slightly concave just behind the nostrils and ended in a point. The feet were some of the most specialized of enantiornitheans where all the toes were of the same length.

Currently there are seven genera listed under the longipterygid family clade with one species within each genus. The genera are: Longirostravis (Lon-gee-row-stray-vis) from ~125 mya; Shanweiniao (Shan-way-now) from 122 mya; Boluochia (Bwaw-lwaw-chuhr-uh) from 121.6 mya; Longipteryx (Lon-gip-ter-ix) from 120.3 mya; Camptodontus (Camp-toe-don-tus) from 120 mya; Shengjingornis (Shen-jing-or-nis) from 120 mya and Rapaxavis (Rah-pax-uh-vis) from 113 mya. All lived during the Early Cretaceous in what is now the ‘Jiufotang’ and ‘Yixian’ formations of China.
Credit: PNG Clipart  Longirostravis
As the earliest known longipterygid, Longirostravis from its cranial morphology, provides the first evidence among avian theropods of a probing feeding behavior in foraging for food. This specialized type of feeding behavior had not been taken advantage of among other basal bird lineages which is now a main source of feeding habits among shorebirds and woodpeckers.

The word, ‘longirostravis’ is Latin meaning, ‘bird with a long rostrum’. The rostrum, or snout was long and slightly curved at the tip while supporting five pairs of small conical teeth. Most likely the snout was used for probing in mudflats to get at small crustaceans or shellfish. The sternum was unusually shaped and was much like moose horns with a pair of three-pronged projections. No more than 17.8-22.9cm/7-9in, Longirostravis was no bigger than the extant bobwhite quail.
Artist: Scott Reid  Shanweiniao
Meaning ‘fan-tailed’, Shanweiniao had tail feathers arranged in the pygostyle that could be fanned out to serve as a rudder giving a much stronger flight capability. The wing structure was also patterned to create strong lift from taking off and strong uplift during flight. Due to narrow spacing in between the tail feathers one study concludes that the tail feathers were more rachis (central shafted in pennaceous feathering) dominated. The wing feathers most likely allowed dexterous maneuverability within trees.
Artist: Sydney Mohr  Shanweiniao
As in the unique longipterygid characteristics in having a long snout, the rostrum just exceeded 62% of the total skull length. The whole of the cranium shape was elongate as well. Shanweiniao most likely probed tree bark for insects and grubs and was small at around 8cm/3.2in minus the tail feathers. The teeth decreased in size from front to back.

Artist: Daniel Bensen  Boluochia
Boluochia is closely related to Longipteryx and was once thought to be a juvenile specimen of Longipteryx, but the fourth metatarsal on each foot diverges significantly from the others, causing the outer toe to be separated from the rest when perched. This is a feature among longipterygids that is only found in Boluochia.  Along with, Longipteryx, Boluochia represents the more basal lineage of longipterygids in possessing larger manus (hand) claws and bigger teeth than the more derived other longipterygid members. At ~19.1cm/7.5in, Boluochia was about the size of the extant wood thrush.

Credit: Nix Illustration  Longipteryx
Longipteryx means ‘long-winged bird’ and at 15cm/5.9 long excluding the tail, Longipteryx had proportionally long wings as compared to the body that supported two long separate fingers ending in claws and a stubby thumb on each wing. Unlike most other avian theropods of its time, Longipteryx had bone extensions called, uncinate processes that strengthen the rib cage by extending out caudally from each rib.

Longipteryx is the dinosaur theropod equivalent of a modern day kingfisher as it was a well-equipped aquatic feeder to dive, nab small fish or crustaceans, then fly back up to perch on a tree and consume its meal.

The enantiornithean, Camptodontus is not to be confused with a beetle genus of the same name and the species name for an Astragalus plant. The term means, ‘bent tooth’, but is currently the unofficial name for this distinct enantiornithean.
Artist: José Carlos Cortés  Camptodontus
With the body form of a duck, Camptodontus was 25cm/9.8in long with a wingspan of 50cm/20in. Camptodontus surely was an aquatic theropod frequenting shorelines in search of small to mid-sized fish. The legs were short and the forelimbs supporting the wings had claws. The head was long for its body including an extremely long snout supporting large recurved teeth in the jaw tips that protruded from the jaws. The well preserved fossil remains display a close relationship to Longipteryx.

Artist: Jack Wood  Shengjingnornis

The body length of Shengjingornis was 20cm/7.9in with a wingspan a little over the body length at 22cm/8.7in. In contrast to the body, the legs were long distally ending in curved claws, while each of the wings possessed three short curved claws. The wing features, including a cake-like sternum, indicates it was a strong flapping theropod. With a bent downward snout ending in rather large sharp conical teeth just in front of the nasal alludes to a fact that this longipterygid was a specialized feeder. But what it fed on is strictly speculative; however, it is possible that it was well equipped to probe tree bark for insects, grub worms and other invertebrates. Or, but this is really stretching it, skim the surface of bodies of water to ensnare and trap small fish, aquatic insects and crustaceans.
Shenjingornis fossil
In addition to its unusually shaped sternum, Shengjingornis also possessed a Y-shaped furcula, a caudally distributed keel and a caudally concave coracoid. These unique morphological features indicate that Shengjingornis held an intermediate evolutionary position among its longipterygid relatives.
Artist: Jack Wood  Rapaxavis
Rapaxavis was another smaller longipterygid with a body length of 17cm/6.7in supported by a larger tail 30cm/11.9in long and by a wingspan of 25cm/9.9in. The long part of the tail consisted of two ribbon-like feathers that made up most of the tail length and was sexually dimorphic featured only in males.
Rapaxavis fossil
The fossil remains reveal the caudolateral processes of the quadrangular-shaped sternum possessed two prominent branches forming a V-shape ending into one small xiphoid (lowest division of sternum) branch. As a character of enantiornitheans, a procoracoid is absent. Although gastralia were preserved in the proximity of the pelvic girdle, there is no evidence of uncinate (hook shaped) processes that usually accommodate gastralia.

One item noted in the fossil remains of Rapaxavis is that it is the only exception within the whole clade of enantiornitheans that the derived manus (hands) lack unguals (pertaining to claws, nails or hooves), even though it possessed keratinous sheaths of the pedal unguals. Also, like the enantiornithean Concornis, Rapaxavis possessed a pair of paracoracoidal ossifications (pectoral bones). No one as yet knows the exact function of these bones and within the entire clade of Avialae, these are the only two species that possess this unique ossification.
Rapaxavis skull
The name, Rapaxavis means ‘grasping bird’ and equipped with long legs and curved claws that were well suited for grasping and perching on limbs, it too, could navigate efficiently while flying through forests. It was most likely a forager of invertebrates, especially insects collecting them in arboreal and ground settings.
One last, enantiornithean I would like to discuss before going to birds, is in the Euenantiornithes six genera family of, Avisauridae (A-vuh-sor-uh-day); it is Halimornis. The avisaurids temporal range was from 125-66 mya ending during the last extinction of dinosaurs.

With a temporal range of 80 mya during the Late Creatceous, a body length of 17cm/6.7in, a wingspan of 40cm/15.8in and with the fossil remains found in Alabama’s ‘Mooreville Chalk Formation’, Halimornis, as in most all avisaurids, was among the largest, most diverse and last of the enantiornitheans.
Artist: Scott Reid  Halimornis
Halimornis (How-lee-mor-nis) flew and glided among the air currents above the ancient Western Interior Seaway’s coastline 80 mya. It is the only enantiornithean that would be considered an ocean going species. The holotype fossil was found in sedimentary rock that would’ve been miles away from land. It also had unique wings that would’ve made it adept at swimming. The diet, most likely consisting of fish filled a small niche during this time period.

A young hatchling enantionithean encased in amber
We’ll leave enantiornitheans with a newly discovered Burmese amber fossil find of a 99 mya hatchling initially designated in the genus, Belone. Coming from the ‘Hukawng Valley’ in northern Myanmar, the fossil measures no more than 7.6cm/3in and is one of the most complete amber fossils coming from Mayanmar. Already possessing tiny conical teeth, it was no more than a few days or couple of weeks old. With great detail, the wings, feathers and skin have been preserved. Belone has already been assigned to a genus of needlefish, so the naming for this theropod enantiornithean will eventually change.                                  

It has gotten to the point with many new discoveries and anatomical analysis that maybe the phraseology shouldn’t be bird-like dinosaur, but dinosaur-like bird.
Theropodal evolution to bird
As paleontologist, Mark Norrel has stated, “Many of the animals that were thought to look like giant lizards only a few years ago are now known to have been feathered, to have brooded their nests, to have been active, and to have had many other defining bird characteristics, like wishbones and three forward-facing toes. To this list we can now add that the precursors of birds were also small, primitive members of a lineage that later grew much larger long after their divergence from the evolutionary stem leading to birds.”

The common ancestor to modern birds diverged from other paravians around 95 mya. Molecular biology confirms this. Anatomy confirms this and paleontology confirms this…not only did birds speciate from ancestral dinosaurs...birds are dinosaurs. In fact, T. rex is more closely related to the chicken in genetics and time than it was to the earliest true dinosaurs. Gallus jungle fowl appeared 50 mya, while T. rex reined 68-66 mya; the first dinosaur appeared 231.4 mya. So as you see, there is only a difference of 16 million years between T. rex and the Gallus jungle fowl, while T. rex showed up 163.4 million years later after the first dinosaurians appeared.   

Genes in birds are very much like dinosaur genes, it’s just the sequence that varies in what genes have been switched on and what has been switched off. Bird embryos carry an exacting average of caudal (tail) vertebrae as dinosaurs had. As the embryo further develops, the gene for tails is switched off with the tail vertebrae being absorbed for building blocks somewhere else in the developing fetus. Chickens early on in fetal development possess tiny teeth that barely erupts the gum line, but then are switched off from further development and are absorbed. On a regular basis, molecular biologists inject a viral component into developing chicken embryos that maintains the switch, switching it from off to stay on, thus further developing the embryo’s teeth. Upon hatching, the chick has a well-stocked mouth of teeth that not only appear shaped as theropod dinosaur teeth, but in positioning, are recurved backwards like theropods.

Female birds grow a special type of bone in their limbs between the hard outer bone and the marrow. Called the medullary bone, it is rich in calcium and is used up in making eggshells during breeding. The female birds that produced it reabsorb calcium when they have finished laying eggs in rebuilding the medullary for the next breeding season. Medullary bone has also been found in many theropod fossils from allosaurs, tyrannosaurs and tenontosaurs, which also aids in determining the sex of the fossil remains. The medullary also has shown up in female subadult fossils indicating sexual maturity was reached before adulthood, just like in humans.

The skeletal anatomy, morphology, physiology and behavioral evidence conclusively place birds within the evolutionary radiation of theropod dinosaurs. With respect to growth and energetic physiology, the first birds were simply feathered dinosaurs. The evolution of the novel bird pattern in modern forms occurred later in the group’s history. As the result, modern birds are the most speciose amniote with well over 10,000 species.

Although ornithischian filaments and theropod proto-feathers are not obvious in birds, dinosaurs were the first animal to support feathers. Reptilian scales evolved 320-310 mya; dinosaurs retained them and passed scaled legs over to birds.

Now, with over 10,000 extant species, with this much diversity, birds by far outnumber extant mammals and reptiles two to one, so let’s get to ‘em.

Euornithes (E-u-or-nah-theez) ~ is the clade leading directly to modern birds. This is the line of theropods that became what we think of as birds. So, all feathered and toothless theropods capable of flight and all modern birds with the exceptions of penguins and palaeognaths (flightless ostrich-like birds) belong to this group. Therefore, it also includes the most common recent ancestor to all modern birds. The temporal range is from 130.7 mya to the Present.

Euornitheans are the first true birds; in fact Euornithes means ‘true bird’. Feathers, a short fused pygostyle, toothless beaks, clawless forelimbs, hollow bones, wrist joints positioned for flapping wings, a bastard wing, air sacs, tridactyl feet/hands, homeothermy, cranial kinesis, smaller size, female medullary bone, brooding and perching all first evolved in earlier theropods to culminate into an animal we call bird. These adaptive evolvements were originally not intended for flight, but through natural selection and speciation came together and gave us the bird.
Evolution of the theropod manus (hand)
Dactylos is Greek rooted referring to finger or toes. Therefore to wit: Oligodactyly ~ less than (<) five digits; Polydactyly ~ more than (>) five digits. In birds as oligodactyl, digit V (pinky finger) on the outside of the hand appears first during embryonic development, but evolves and develops into digit IV (ring finger). It is also shown in studies that in digit I (thumb), an embryonic finger begins to develop but quickly disappears. So, final finger development of the embryo is in the fully-formed digits II, III and IV (the index, middle, and ring fingers). This of course was inherited from their theropodal ancestry in having tridactyl (three digit) manus (hands) and pedes (feet). Therefore, in euornitheans and henceforth onward, all birds are distally three digited.

The avian respiratory system plays a role in thermoregulation while the lungs are much smaller when compared to other vertebrates, but are supported by nine theropod inherited air sacs that play a big role in respiration. Due to air sacs allowing for a unidirectional flow of fresh air into the lungs, the lungs are constantly supplied with oxygen. So as air sacs fill, the lungs are also filling, but as air sacs and the lungs empty, the air sacs empty into the lungs keeping them oxygenated with a constant supply of fresh air.
Bird air sacs
There are around four holotypic species of euornitheans with one added holotypic species as a sister subgroup to the ornithuromorphan clade. Ornithomorpha (Or-nith-o-mor-pha) is the most inclusive clade containing extant birds. With a temporal range of 130.7 mya to the Present, it is divided into three holotypic genera, one holotypic genus as a sister subgroup, two families and one holotypic genus as a sister subgroup to the clade, Ornithurae (Or-nith-ew-ray or Or-nith-ree). Ornithurines are further divided into two related holotypic genera, one clade and all the thousands of species contained in Aves (A-veez), which includes all modern birds. I would like to note here that Neornithes (Nee-or-ni-theez) is becoming the more popular term in replacing Aves.

The basal euornithean holotypic genera are, Archaeorhynchus (Are-kay-o-rin-cuss) from 125-120 mya; Jianchangornis (Jeye-uh-chan-gor-nee-is) from 120 mya; Zhongjianornis (Zhone-gee-jeye-or-nis) from 120 mya and Chaoyangia (Chai-yang-nee-uh) from 120mya. The ornithuromorphan genus sister group is Schizooura (Ski-sue-u-rah) from 120 mya. These are the most primitive euornitheans; a few even retained a few teeth and small manus (hand) claws. But even though they are considered proto-birds, they had more in common morphologically, physiologically, anatomically and in physical functionality with modern birds than with Sinornis or any other enantiornithean. All their fossils originate in China.

With the fossil remains coming from the ‘Yixian Formation’, Archaeorhynchus’ fossils display well preserved complete skeletons measuring 20cm/7.9in long. Even associated with the head, neck and tail regions, feathering was preserved. It is one of the earliest known ornithuromorph that had a toothless β-keratin beak (proteins made from both fibrous and matrix components).
Artist: Brian Choo  Archaeorhynchus
Formed by the fusion of the two clavicles, the U-shaped furcula (wishbone) was robust and in addition with a strengthened keel for flight muscle attachments along the length of the breastbone suggest that Archaeorhynchus was a strong flier. It had three fingers ending in small slightly curved claws. The phalangeal formula was 2-3-2 showing that the middle finger had three phalanges where the two outside fingers had two each. The forelimbs were larger than the hind limbs.

Numerous gastroliths (stomach stones) were found and with the amount shows that the stones were intentionally swallowed and not incidental. This suggests that it was an herbivore.
Archaeorynchus fossil with feather pigment
What is most exciting about the Archaeorhynchus fossil finds is that one of them still possessed preserved lung tissue showing it to be very similar to modern bird lungs. It also had slender curved vertebral ribs that were not attached to the breastbone, but were fully secured at their base.

Artist: Scott Reid  Jianchangornis
Jianchangornis, with its complete skeletal fossil remains found in the ‘Jiufotang Formation’ represents a subadult with a body length of 34cm/13.4in and a wingspan almost double that of 64cm/25.2in. The mouth was lined with 16 tiny conical teeth on the dentary (anterior bone of the lower jaw). A predentary bone (extra bone in lower jaw extending the dentary) is present. Manual digit I extends beyond digit II by ~ 3cm/1.2in with an enlarged metacarpal I taking up most of the length.

Jianchangornis fossil
With a triangular skull and with teeth for grasping are a good indication that it was a piscivore eating small fish by foraging along lake shorelines either by inspecting shorelines for washed up dead fish or by swimming and snagging live prey. With its leg lengths it would have been a good surface swimmer, but not very effective in being a wader. In possessing long wing feathers giving an advantage for a large surface area, Jianchangornis would have been a strong flier.
Artist: Jack Wood  Zhongjianornis
The length of Zhongjianornis was ~ 33cm/13in which was a moderate size for basal euornitheans. Zhongjianornis represents one of the most basal known birds thus far. It predates the pygostylian, Confuciusornis and even predates the split between enantiornitheans and euornitheans. However, there were more numerous similarities between it and the other basal euornitheans.

Zhongjianornis fossil
The jaws of Zhongjianornis were toothless while the beak was pointed. The fossil was found in ‘Jiufotang Formation’ sediment that once was a lake bed, possibly suggesting that it was aquatic and with the shape of the beak was piscivorous. Nonetheless, the feet possessed large claws instead of webbing, so if it was a piscivore, it would dive to snatch fish near the surface or in very shallow waters.

Artist: ©Daniel Benson  Chaoyangia
Chaoyangia, with its fossil also found in the ‘Jiufotang Formation’ as other basal euornithean discoveries and physiologically possessing related features to euornitheans, even close similarities to Zhongjianornis anatomically, was unique in having two dorsal processes on the ischium, the curved bone forming the base of each half of the pelvis. Including the tail, at ~ 16cm/6.2in, it was comparable to the small size of a house sparrow.

Chaoyangia fossil
The keel, an extension of the sternum (breastbone) was well developed. Apophyses (singular: apophysis) are normal bony outgrowths arising separately from other bone centers fusing eventually with the bone over time during maturation. Uncinate hooked processes are extensions of bone that project caudally from the vertical segment of each rib. Chaoyangia’s fossil displays ribs with uncinate apophyses. When compare to other primitive birds, the metatarsals were significantly fused. The dentary (anterior portion of lower jaw bone) were straight and toothed.

Artist: Jack Wood  Schizooura
With similar anatomical characteristics to ornithuromorphs, Schizooura is a sister group to that clade. Being one of the larger euornitheans, Schizooura, which means ‘split tail’ was 55cm/21.7in long, including the tail and had a wingspan of 65cm/25.6in. The arrangement of the tail feathers were such giving the appearance of being split, but in superficially resembling the ribbon tail feathers of earlier avialans, the tail feathering actually fanned out during flight as in modern birds, but forking down the middle. The tail fan would have been somewhat of a hindrance for flight, so most likely served as a display.

Schizooura fossil
Also from the ‘Jiufotang Formation’, Schizooura frequented forest within the trees and ground. The broad rounded wings would have allowed it navigate through forests and with its long legs and short robust toes would have made it ideal to forage on the ground for grain and seeds and perhaps a few arthropods. The skull was triangular ending in a pointed and toothless beak.

Two other basal euornitheans have been discovered and they are: Patagopteryx (Pat-ah-gop-tuh-rix) and Vorona (Voe-roe-nah). Their fossil remains were found outside China proving to be a bit unusual in form anatomically.
Artist: Jaime Chirinos  Patagopteryx following sauropods 
Patagopteryx was found in Patagonia, Argentina’s ‘Santonian Bajo de la Carpa Formation’ in strata from 80 mya. It was a heavily built basal and large euornithean at 60cm/23.6in long.

Patagopteryx internal anatomy

Patagopteryx skeletal
This euornithean had stout robust hind limbs with fused bones in the feet that had four facing forward toes. Along with short femurs, all this alludes to the fact it was a runner, as its wings were reduced and would’ve been incapable of lifting the 2.2kg/5lb body of Patagopteryx. It also devolved the wishbone for flight muscle attachment. Termed ‘secondary flightless’, Patagopteryx is one of the earliest birds to lose the ability of flight, even though the ancestors it came from flew.

Patagopteryx could’ve been an herbivore, or a carnivore, or even an omnivore as its hard beak could’ve sufficed any diet. Also, the second toe had a curved claw, but unlike velociraptors it wouldn’t have been useful as a weapon.

Due to the fragmentary 70 mya fossil remains from the ‘Maevarano Formation’ in Madagascar, Vorona phylogenetic classification is difficult to determine, but it’s clearly a basal euornithean and may later after further study, or other fossil finds even be classified as a basal ornithuromorph.
Artist: Hyrotrioskjan  Gargantuavis
We’ll finish off with one odd euornithean and that is, Gargantuavis (Gar-gan-choo-a-veez). With a temporal range between 73.5-71.5 mya it was found in Europe in three local southern French sites and one in northwestern Spain. During the Late Cretaceous, this region of present day Europe was an isolated island called the, Ibero-Armorican Island in the prehistoric Tethys Sea.

By far in being the largest euornithean, Gargantuavis was ~ 2.2m/7.3ft in total length and weighed in at ~ 140 kg/310 lbs. It thus far, is the largest known bird of the Mesozoic Era. With reduced wings, it was nonvolant (incapable of flight) as considered secondarily flightless. Even though it had a rather broad pelvis, the hips were narrow and bird-like, still though, the girth of the hips prevented the two ilia (singular: ilium which is the upper part of bone forming each half of the pelvis) from meeting. The acetabulum (hip socket) was set close to the front rather than more towards the middle of the pelvis. Osteological studies on its remains show that it had a rapid early growth spurt followed by an extended period (~ 10 years) of slow cyclical growth before attaining skeletal maturity.      

Sedimentary and mineralogical studies affirm that its habitat consisted of episodes of semi aridity and seasonal climate. This, in conjunction with living on an isolated island archipelago land mass, natural selection evolved Gargantuavis into unique traits. This fact, made it difficult to classify as it had no lineage and was not related to the ratites such as the extinct moa or extant ostrich. However, the bone studies showed an avian/euornithean nature in osteological features.   

Ornithuromorpha is the most inclusive clade containing extant birds and was the most derived avian group during the Early Cretaceous. Ornithuromorphans range from 130.7 mya during the Early Cretaceous to the Present. From the primitive ornithuromorph to modern birds, ornithuromorphan birds have a temporal range from 130 mya to the Present.
Ornithomorpha cladogram
Most all the basal ornithuromorph fossil finds come from China and Inner Mongolia. In basal ornithuromorphs, bone histology studies of subadults show that sexual maturity occurred in females prior to skeletal maturity, in which required at least a year to reach adulthood. This is exemplified by the finding of medullary evidence while bone growth was still maturing in fusing. This leads extant bird maturation strategies to go all the way back to non-ornithurine avialans during the Early Cretaceous. In other words, like humans, birds sexually mature first before attaining adulthood.

Currently, there are around twenty known basal holotypic ornithuromorphs and two families with their genera. Some holotypes are: Ambiortus (Am-be-or-tus) from 130 mya; Yumenornis (U-men-or-niss) from 125 mya; Eogranivora (E-aw-gran-e-vor) from 125 mya; Changzuiornis (Chun-su-e-or-niss) from 122.1 mya; Bellulornis (Bell-ull-or-niss) from 120.5 mya; Gansus (Gan-souss) from 120 mya; Iteravis (I-tur-a-vuh) from 120 mya; Jiuquanornis (Jee-kin-or-niss) from 119 mya; Changmaornis (Chun-ma-or-niss) from ~102.5 mya; Apsaravis (App-sar-a-vuh) from 78 mya and Alamitornis (Al-uh-me-tor-niss) from 70 mya. There is some questionable research on whether the Iteravis fossil is actually another fossil specimen of, Gansus. Further research will determine the actual classification.

Artist: Nobu Tamura Eogranivora
Discovered in the Early Cretaceous’ Aptian Stage of China’s ‘Yixian Formation’, Eogranivora means, ‘early granivore’ (diet of seed/grain) with its specific name,   edentulata in reference to ‘edentulous’ (toothless). The scientific name infers that Eogranivora was granivorous with the diet consisting primarily of seeds and grain with a toothless beak. The fossil remains sustained evidence of the crop containing seeds while there were preserved gastroliths in the ventriculus (gizzard). It still retained earlier basal euornithean vestiges of two small slightly curved claws on each manus as phalanges II and III.

Initially, the fossil remains of Eogranivora was first misidentified as Hongshanornis, but after further observations it was noted that the remains detailed longer wings, was edentulous, had stouter shorter legs with the backward pointing digit I (commonly known as the perching toe while technically known as the hallux) and the first metatarsal were missing, thus having only three forward pointing toes in digits II, III and IV. This, as compared to modern birds, suggests that it was more terrestrial rather than arboreal. However, the legs wouldn’t have had the efficacy to run fast, but with fairly developed wings it would’ve flown off instead trying to outrun any danger.
Eogranivora  fossil
Eogranivora had a length of 25cm/9.8in which was around the size of a pigeon. In the skull, the maxilla tapers rostrally articulating dorsally with the premaxilla. In the dorsal beak the long and narrow nasals were medially separated from the dorsal surface of the premaxilla.

With the evolution of flight, Eogranivora is a direct link of Early Cretaceous birds to modern birds and has produced associations into the trophic habits and digestive abilities of early birds and their closest relatives to extant birds. Information from its fossil reveals the changes in the digestive system that occurred with the evolution of flight, through the structural changes of a lighter digestive system.
Artist: Mark A. Klingler  Gansus
The Gansus fossils were found in an ancient lake bed in the province of Gansu, China. At 30.5cm/12in long it was an aquatic freshwater bird that waded through water much like a duck and as a piscivore dove for fish. Some fossils still retained the webbed imprints and remains of fish in the gut region. On average the body length was 30.3cm/11.9in.

Although the wings were slender and incapable of vigorous flight, they still retained flight feathers and were just long enough with a stout sternum to be volant (capable of flight), but short enough to be held back against the body during dives.

With elongated manus (hands), the wing-bones of Gansus were thin, indicating with unstiffened wings, a more gracile flight pattern rather than a strong burst of flapping. The pedes (feet) had interdigital webbing, making it one of the first birds to utilize more efficient aquatic propulsion.
Gansus fossil
Showing similarities with today’s grebes, Gansus pelvic limb length proportions are in stride with extant birds. However, in being three to four separated diversions away from modern birds, Gansus is no direct ancestor to extant birds. But it surely had phylogenetic relations with the direct ancestors to modern birds.

Earlier, we mentioned the comparison between Gansus and Itreavis fossils and how initially researchers first thought they were one and the same species. In comparing the above comparison between one of the Gansus fossils and the fossil of Itreavis, you can see how at first it was misidentified.

Artist: Scott Reid  Ambiortus
The holotype fossil remains of Ambiortus came from the ‘Andaikhudag Formation’ of central Mongolia, which has strata dated from 136.4 to125 mya. The fossil is estimated to be ~ 130 million years old, in which also contains wing impressions.

At 40.1cm/15.8in, including the tail, Ambiortus was a smaller ornithuromorph. Classifying it has been tough as its fossil showed morphological similarities with enantiornitheans and ornithuromorphs. However, further studies conclusively put it in as a basal ornithuromorph as it was overall more derived than earlier forms. Yet, coming from 130 mya strata does push ornithuromorphs back another 5 million years plus.

Some ornithuromorph features in Ambiortus are: possessing a rectangular medially projecting procoracoid, coracoid with a lateral process, U-shaped furcula, curved scapula, rounded deltopectoral crest and a sternal keel just reaching the rostral margin of the sternum. It was closely related morphologically to Apsarvis.

The ornithuromorphan family, Hongshanornithidae (Hun-shawn-or-nith-ah-day) had a temporal range of 130.7-120 mya. Hongshanornithids were small ranging in size from 10.2-11cm/26-28in which includes the tail. The legs were long in comparison to the body and most likely were shorebirds. All possessed a snout with teeth mostly in the upper maxilla and lower dentary and still possessed forelimb claws. As far as relations to other ornithuromorphs, hongshanornithids were most closely related to the other ornithuromorph family, the songlingornithids.

There are five holotypic genera in the family, Hongshanornithidae and they are: Archaeornithura (Are-kay-ore-nith-ura) from 130.7 mya; Tianyuornis (Tea-an-you-or-niss) from 125 mya; Hongshanornis (Hun-shawn-or-niss) for which the family is named after, from 122 mya; Longicrusavis (Lawn-guh-crew-say-viss) from 122 mya and Parahongshanornis (Pah-rah-hong-shawn-or-niss) from 120 mya. All lived during the Early Cretaceous.

The fossil remains of Hongshanornis were collected in the lacustrine deposits of the ‘Yixian Formation’ of Liaoning Province, China. With a body and tail length of 18cm/7.1in and a wingspan of 32cm/12.6in, it was on the smaller end in ornithuromorph size. The fossils are detailed in showing miniscule teeth impressions in the front of the mouth and one small thumb claw on each wing. Some of the fossils still retain bone tissue and feathering. Even though the tiny rounded teeth and claws show a persistent remnant of ornithuromorph dinosaurian ancestry, the reduction in amount and size prove that ancestral theropodal dinosaurs had radiated out in setting the anatomical plan of birds.
Artist: Jack Wood Hongshanornis
Hongshanornis flit and flew about much like small birds do today. Due to the flight anatomical arrangement of the wings, it could also continuously flap at slow speeds while alternating and flexing the wings at high speeds. Its tail fanned and was most likely a shore bird with its long thin legs.

Hongshanornis fossil
The Hongshanornis rounded skull lowly constricts into a pointed rostrum (beak-like projection). In the fossils, ribs are preserved articulating with the sternum. Proximal ends of the thoracic ribs are robust while the expanded proximal portion abruptly narrows towards the much thinner shaft. As in most ornithuromorphs, the furcula is U-shaped.

Hongshanornis most likely had a generalist diet relying on insects, invertebrates along shores of aquatic environments, invertebrates living within the shore mud and with the evidence of gastroliths in one fossil, hints to the fact that it supplemented its diet with plants.
Artist: Stephanie Abramowitz  Longicruavis
Longicrusavis was ~ 14.5cm/5.7in in body length with its fossil remains coming from the ‘Yixian Formation’ of Liaoning Province, China. Closely related to Hongshanornis, it too had long skinny hind limbs, but unlike Hongshanornis, its rostrum was more robust and the skull was triangular in shape as opposed to being rounded. The nearly complete fossil includes carbonized feathering with visible coloration around the skull and forelimbs. The snout was long and thin; however it was evolving into a beak with no teeth or evidence of alveoli (teeth sockets) in the mandible. It also possessed large eye sockets.

Longicrusavis Fossil
With the hind limbs being substantially very long in relation to the forelimbs, as in Hongshanornis, suggests that Longicrusavis frequented shallow lake shorelines. The name actually highlights this in meaning, ‘long shin bird’. Teeth were present in the maxilla and premaxilla. All this would imply that it went after insects frequenting the shorelines and invertebrates living along shorelines. For improved flight, Longicrusavis had evolved long fanned tail feathers.

Songlingornithidae (Song-lin-gor-nith-ah-day) family members had a temporal range of 125-75 mya. Songlingornithids are characterized by having a pair of medial fenestrae (openings) in the caudal margin of the sternum. The metatarsals are also fused into a tarsometatarsus (fused lower leg bone of birds and some non-avian dinosaurs). Also, songlingornithids possess on the premaxilla at the tips of the lower jaws ossicles (tiny bones) of unknown functional significance. Most all songlingornithids come from the ‘Jiufotang Formation’ of Liaoning Province, China with one Yanornis species coming from the ‘Yixian Formation’ and Hollanda coming from Mongolia’s ‘Barun Goyot Formation’. Only Hollanda comes from the Late Cretaceous, the rest come from the Early Cretaceous.

There are four songlingornithids and they are: Yanornis (Ya-nor-niss) from 124-120 mya; Songlingornis (Song-lin-gor-niss) from120 mya; Yixianornis (Yix-e-an-or-niss) from 120 mya and Hollanda (Ho-lawn-duh) from 75 mya.
Artist: Jack Wood  Yanornis
Yanornis was one of the first songlingornithids to show up 124 mya ago. Its fossils, all found in the ‘Jiufotang Formation’, show that it lived in a forested section near bodies of water. Capable of flying, it also spent a lot of time frequenting shorelines on the ground and was most likely a wader. Rather small, it measured no more than 10cm/3.9in in body length.

Yanornis fossil
It had at the tip of the snout a toothless beak where the rest of the snout contained ten teeth in the upper jaws with twenty in the lowers. Although in the fossils there is an absence of the prefrontal bone and the skull wasn’t diapsid (common traits of ornithuromorphs), Yanornis’ scapula (shoulder blade) and coracoid (paired bones in shoulder assembly) however, had evolved the basic assemblage as in modern birds; therefore, it was capable of lifting its wings far above its back for efficient up stroking.

Yanornis fossil with predigested fish
There was initial debate on what the diet of Yanornis was. In one fossil find there was evidence of gastroliths leading some researchers to declare it an herbivore. But later studies in proving the stones weren’t gastroliths, just random stones in the intestines that impacted from incidental sand ingestion. But a more recent finding of another fossil that showed fish remains in the crop and digested fish in the stomach, conclusively pointed out Yanornis was a eater of small fish; a piscivore.

Artist: Luis Chiappe  Hollanda
Hollanda was ~ 40cm/15.8in and with its very long legs and toe configuration would’ve appeared as a smaller roadrunner that also could run fast; hence it was a ground dweller. The lithology of the strata Hollanda’s fossil came from, portrays an environment that would’ve consisted of sand dunes stabilized by a covering of vegetation with a continuous water supply that formed shifting streams and ponds.

This songlingornithid appearing towards the end of the Late Cretaceous shows that basal/primitive ornithuromorphs, even though they all went extinct by the end of the Cretaceous, held a long succession rate due to their evolutionary ability to fill ecological niches whether it was in the air, water or ground. Through natural selection, they adapted quickly in the geological record. Hollanda was a ground dweller and likely spent most of its time near bodies of water in a semi-arid environment in search of small vertebrates like lizards and invertebrates like large insects. It would run before it would fly away from danger.

Initially, Hollanda was considered more advanced and placed as a sister group to Ornithurae, but later studies proved it was phylogenetically related to the more primitive ornithuromorphs as a basal songlingornithid.                                   

Ornithurae is Greek meaning ‘bird tail’ and includes the common ancestor to Ichthyornis, Hesperornis, Limenavis, all other basal holotypic ornithurans and of course all modern birds (Neornithes). The ornithuran temporal range is from 121 mya to the Present. Most all ornithurans were aquatic.

Ornithurans have autapomorphies that are distinctive features as derived phylogenetic traits originating from the Ornithurae common ancestor. The ornithuran cladogram includes all taxa more closely related to extant birds than to Archaeopteryx morphologically, physiologically, phylogenetically and for sure, anatomically.

Most ornithurans had reduced wings that could not support aerial transit opting to forego flight for an aquatic life. The wings were used for paddling or held tightly up against the body for diving to lessen resistance then utilized for maneuvering underwater. All ornithurans either had lobed or webbed feet for aquatic propulsion in being the first line of dinosaurs to enter into marine environments.       

All the ornithurans’ adaptations to an aquatic life indicate a long evolutionary history prior to their Late Cretaceous life. As a monophyletic clade, ornithurans, even though they were water fowl in both freshwater and marine, they are the closest relatives to all living birds.

The Late Cretaceous toothed ornithuran birds, Ichthyornis and Hesperornis fossils preserve remains that are essentially indicative of modern bird bone tissue demonstrating the fact that the unique growth strategy of living birds evolved during the Cretaceous before Neornithes. Furthermore, histological analysis of most basal birds from the Early Cretaceous (ex: Sapeornis, Jeholornis) and basal ornithuromorphs from the Late Cretaceous reveal slower forming bone tissue and lines of arrested growth (LAGs) indicating that the fully modern growth strategy evolved within the clade Ornithuromorpha’s early basal representatives.
Under Ornithurae, currently there are around twenty plus species, but essentially there’s one basal holotype in, Ichthyornis (Ick-the-or-niss) from 93-83.5 mya; Hesperornithiformes (includes all hesperornithiforms) where there is one distinct hesperornithiform holotype in Chupkaornis (Choop-kah-or-niss) between 89-85 mya; one subgroup clade in Hesperornithes (Hess-per-or-nah-theez), which consists of six holotype genera and one family in
Enaliornis (E-nal-e-or-niss) from 99.6-93.5 mya;
Pasquiaornis (Pas-qwee-a-or-niss) from 93 mya with two species;
Baptornis (Bap-tor-niss) from 83.5-80.5 mya;
Brodavis (Brod-a-vis) from 80.5-66 mya consisting of four species;
Judinornis (Ju-dee-nor-niss) from 70 mya;
Potamornis (Poe-tah-mor-niss) from 66 mya;
Hesperornithidae (Hess-per-or-nith-ah-day) from 85-82 mya with five genera
Fumicollis (Fu-me-col-liss) lived between 86-82 mya;
Parahesperornis (Par-ah-hess-per-or-niss) lived between 85-82 mya;
Hesperornis (Hess-per-or-niss) from 82-78 mya;
Asiahesperornis (A-Shah-hess-per-or-niss) from 70 mya:
Canadaga (Can-ah-day-gah) from 67 mya.  

Finally, in rounding out Ornithurae there is one holotype sister group, Limenavis (Lye-men-nay-viss) to Neornithes (Nee-or-nuh-theez) or Aves (Ah-vez), whichever name you prefer.
Artist: Jack Wood  Ichthyornis
The basal ornithuran, Ichthyornis was a seabird with the name meaning, ‘fish bird’, which didn’t refer to its seafaring ways, but instead, to its bi-concave fish-shaped vertebrae. Fossil remains have been found in the chalk beds laid down during the Western Interior Seaway from Alberta and Saskatchewan, Canada and in the U.S. from Alabama, Kansas, New Mexico and Texas.

At 24cm/9.4in long and a wingspan of 43cm/17in, it was the ecological equivalent to present day seagulls and skimmers. This most basal ornithuran is the only ornithuran to have flight wings. With teeth only in the middle section then back towards the end of the mouth of the upper and lower jaws, the toothless jaw tips functioned as a bird beak. This allowed it to bite like a little dinosaur and peck like a bird. Teeth shape was more flattened than rounded with a broadening base while the tips lacking any serrations slightly curved backwards.

Ichthyornis skull & Skeleton 
For flight muscle attachment, Ichthyornis had an enlarged sternum (breastbone) indicating very strong and long flight capabilities. The skull per body size was larger than its dinosaurian ancestry; a trait found in modern birds with relative larger brain size to accommodate the need for more brain processing during flight. It still retained more muscular jaws than modern birds, however less than dinosaurian ancestors did; an in between holdover from its theropodal lineage. It also on the foot possessed the jointed tarsometatarsal characteristic of modern birds.
Artist: Jaime Chirinos  Ichthyornis stealing fish
Its diet was primarily fish and most likely it would take any ample opportunity as a thief in stealing fish captured by other piscivores as shown above. Ichthyornis might as well have surveyed the beaches for any stranded small molluscs or dead fish to scavenge.

Artists: Mike Hanso, BA Bhullar  Ichthyornis 
The hesperornithiform, Chupkaornis is one of the rarer Asian ornithurans with the fossil remains coming from the marine and sedimentary strata of the ‘Kashima Formation’ in the ‘Yezo Group’ near Hokkaido, Japan. Therefore, it dwelled in shallow coastal waters and is phylogenetically an ancestral sister clade to Brodavis.

Artist: Masato Hattori  Chupkaornis
Around the size of a duck ~ 58.4cm/23in, Chupkaornis was adapted to diving in ocean coastal waters. To assist its evolutionary leap from flying to diving, the wings were reduced to flippers, the hind limbs developed lobed feet interlaced with thin webbing, with the surface of the first digit of the fourth toe showing a distal articulation and the pelvis was morphologically modified with a dorsally directed antitrochanter (articular surface on the ilium of birds). All these features gave limbs geared for aquatic foot propulsion. Although there is no evidence of what it ate, but stochastic processes allude to the fact it was fish and small marine invertebrates.

Hesperonithes was a highly specialized clade of aquatic hesperornithiforms that inhabited marine and freshwater environments. They were so specialized that the hind limbs developed for propulsion through liquid mediums would have been useless for walking on land and most likely were used only for shoving the body ventrally while on terrestrial environments. Even the hip and knee joints were shaped such that hesperornitheans could not move them dorsoventrally. The bones were dense making the animal less buoyant for diving purposes. Morphologically, hesperornitheans had similarities closest to modern day diving ducks and grebes.

The snouts were long and narrow, further narrowing towards the tip which was tipped with a slightly hooked beak. Inside the mouth the jaws were lined with small sharp teeth set in a longitudinal groove unique only to hesperornitheans. The beak tip was toothless. All hesperornitheans come from the Late Cretaceous and diverged from their and birds common ancestor during the Early Cretaceous.
Artist: Nobu Tamura  Enaliornis
Enaliornis is a hesperonithean while representing the most primitive taxon of Hesperinithiformes. Due to this, it is currently the oldest known diving bird. There are three species that occurred between 99.6-93.5 mya just into the beginning of the Late Cretaceous. From near present day Cambridge, England, the fossils come from the former lake beds of the ‘Cambridge Greensand Formation’ composed of marled shales and sandstones. The species are: E. barrette, E. sedgwicki and E. seeleyi. In size, Enaliornis was ~ 54.9cm/21.6in and was more like its earlier smaller sized ornithuran relatives than its larger later hesperonitheans. 

There is no evidence of a toothed snout and the wings with a length from shoulder to the distal end of the body, shows signs of the beginnings of atrophying in displaying vestigial evolvement toward diving purposes as opposed to flying. The toes, although not webbed were heavily lobed as the shapes of the distal tarsometatarsal trochlea (an anatomical structure acting as a pulley) present.
Enaliornis Braincase air pockets
What appears as interesting is the extensive pneumaticity (air spaces within bone) of the skull. The rostral margin of the ventral lamina (bone plates forming a vertebra’s wall surface) of the cranial base is bent due to the resistance of the basisphenoid’s (cranial base) edge. The fossa (shallow depressions in bone) appears formed by the squeezing of the ventral lamina of the base against the dorsal lamina.

Artist: Gunar Björkman  Baptornis
Baptornis, which has only been found in the Niobrara chalk stratum of Kansas, was similar to Hesperornis, but it was a much smaller bird overall with a length ~ 70-90cm/27.6-35.4in and perhaps slightly less well adapted to an aquatic existence. The wings were somewhat larger and the legs and feet slightly less modified for swimming than in Hesperornis. A coprolith (fossilized excrement) most likely derived from Baptornis as it was associated with its fossil, contains remains of a small fish species of the teleost genus, Enchodus that was common in the Niobrara Sea. This, along with Baptornis fossil remains having only been found in formations of former sea sediment, supports the view that Baptornis was a marine piscivore.

Baptornis existed during the rise in ocean waters creating North America’s large inland sea, the ‘Western Interior Seaway’ that stretched from the Gulf of Mexico through the Midwestern U.S. and Canada ending in the Arctic Ocean. Existing from the mid-Cretaceous to the earliest of the Paleocene, this interior seaway was home to Baptornis. With fossil remains found in Sweden where the former, ‘Turgay Strait’ (also known as the, ‘Turgai Sea’) once met the ancient North Sea, Baptornis also occurred there. In fact it may have swam and dove the entire Holarctic.
Baptornis skeletal  Martin & Tate et al
Physically, Baptornis was shaped much like a plesiosaur with a long neck and streamlined short body. Although the wings carried all the flight bones, they were greatly reduced in size becoming vestigial and unable to support flight. With the hind limbs naturally positioned under the body and not firmly along the sides of its body, the feet could’ve pointed forwards to manage small hops or waddle on dry land. Unfortunately there have been no remains of the beak in the fossil discoveries, but as in other hesperonitheans most likely possessed teeth to grasp its slippery and pelagic prey. Known as pachyostosis, its bones were thickened to lessen buoyancy for more efficient diving.

Baptornis consists of numerous adults and juveniles. They have been found along ancient coastal shorelines and deep out into ancient sea sediment. This suggests that this basal hesperornithean was migratory or at least frequented northern islands to breed as that is where most of the juvenile fossils come from.
Artist: Matthew Martyniuk  Brodavis
Brodavis fossil remains have been found in North America and Asia from the ‘Frenchman Formation’ of Canada, the ‘Hellcreek Formation’ and ‘Sharon Springs Formation’ of S. Dakota USA and the ‘Nemegt Formation of Mongolia. There are four species in: B. americanus, B. baileyi, B. mogoliensis and B. varneri. With the fossils discovered in lakebed sediment it is the only hesperornithiform that lived in freshwater ecosystems. This genus averaged ~ 82.3cm/32.4in in length.

Although there is very little evidence of pachyostosis (bone thickening) to negate buoyancy, anatomical features still point to a diving existence along with lobed feet. With thinner bones than its hesperornithean relatives and wing bones that had not yet begin to radically reduce in size as nowhere near a vestigial stage, Brodavis most likely was volant (could fly). All these examples add up to the fact that Brodavis could have lighter bones in freshwater environments because freshwater is less buoyant than seawater and with lakes as much smaller bodies of water than seas, it could also frequent other lakes through flight to satisfy its piscivorous diet.   

All members in the family, Hesperornthidae evolved for a specialized aquatic life along coastal sea shores as well as into deeper offshores. The hind limbs were adapted to propel through aquatic environments, while the wings had become vestigial being incapable of flight. On land however, the hind limbs are attached to the sides of the ilium and would be useless for walking, so at best hesperornithids scooted across solid terrain on their bellies.

Most hesperornithid species come from N. America, but there have also been recent discoveries in Sweden and Kazakhstan where the ‘Turgay Strait’ once was and a very recent 2018 Saratov Province, Russia find of H. rossicus from the sandstone of the ‘Campanian Rybushka Formation’.
The Turgay Strait
There are five genera of hesperornithids and they are: Fumicollis a holotype from the ‘Niobrara Chalk’ of Kansas; Parahesperornis from the upper ‘Niobrara Chalk’ of Kansas; Hesperornis from the U.S. and Canada’s original provenance of the ‘Interior Western Seaway’, Sweden and Russia’s ‘Campanian’ bedrock; Asiahesperornis from Kazakhstan’s ‘Turgay Strait’s sedimentary bedrock and Canadaga from Canada’s Bylot and Devon Islands.

Artist: Jaime Chirinos  Hesperornis
Currently discovered, there are around eleven Hesperornis species and they are: H. altus, H. bairdi, H. Chowi, H. crassipes, H. gracilis, H. lumgairi, H. macdonaldi, H. mengeli, H. montana, H. regalis, and H. rossicus. 

Hesperornis species were rather large averaging ~ 1.8m/5.9ft in length. Although they possessed a keratinized beak, except for the premaxilla being edentulous (toothless) the mouth was rowed with small sharp conical teeth. The beak was used in snatching, while the teeth were utilized in grasping slippery marine prey. The beak had small pits in the upper palate that allowed teeth from the lower jaws to lock into the pits preventing the beak from opening disavowing any thrashing prey to escape.
Artist: John Conway  H. regalis
With the hind limbs, the femur and tibia of the leg were encased within the body cavity with only the ankle on down to the foot exposed. This made the heavily lobed feet stick out sideways perpendicular to the body. This arrangement was excellent for propelling through a liquid medium, but too clumsy and awkward for walking on land.

Artists: Julio Lacerda & Henry Sharpe  Hesperornis as thief & prey
The vestigial wings would have been only useful for steering or acting as a rudder while swimming and diving. The sternum had no keel that is present in birds of flight. The skeletal anatomy was solid throughout to counter buoyancy during diving. The neck of Hesperornis was long and flexible enabling greater ease in capturing darting fish. The lower jaws were not fused as they were united by cartilage for greater flexibility. The forelimbs would’ve been completely covered in skin and feathers.

Hesperornis was a true piscivore predator, but no doubt was an opportunist in scavenging washed up dead fish and even torment other animals in stealing their fish prey.  It appears at times however that Hesperornis was itself on the menu. Discovered in the ‘Pierre Shale Formation’ of South Dakota, among other predigested animals, the partially digested remains of Hesperonis was found in the gut cavity of a large Tylosaurus proriger fossil.
Hesperornis fossils
Hesperornis’ northern realms today would be considered cold waters, but during the Late Cretaceous the waters were subtropical to tropical waters. Even though it is considered to have lived in marine waters, fossils of the youngest specimens were found in the ‘Foremost Formation’ an inland freshwater stratification. As well, the one H. altus fossil was found in freshwater deposits at the base of the ‘Judith River Formation’ in present day Montana.       

The Hesperornis genus countered its avialan ancestry that was trending in smaller sizes to accommodate flight. In foregoing flight for an aquatic lifestyle, later hesperornithids began increasing body size and one of the last hesperornithid species to appear was Canadaga was the largest one of all in the lineage to modern birds. From 1.5m/4.9ft to a whopping 2.5m/8.2ft, Canadaga played second fiddle in size to no other. Almost half that size was the neck.
Credit: Canadian Museum of Nature  Canadaga
Canadaga lived in the shallow seas of the Arctic and even though these waters were much warmer then, it still got cold during the winter. At present, this is the only Cretaceous bird found in Arctic sediments.

Canadaga vertebrae A)Ventral B) Dorsal
The solid central part of a vertebra where arches and processes are attached is known as the centrum. With the Canadaga vertebrae fossils’ centrum having lengths between 25.45mm/1.0in to 26.65mm/1.1in makes for a big bird. The distinction from other hesperornithids is in each cervical vertebra’s transverse process (a vertebral lateral bony projection) possessing a cavity at the base. The femur is slightly arched craniocaudally (from the cranial to the caudal end), a feature unique to Canadaga. Also in the leg, the patellar (kneecap) sulcus (angled narrow grove) was distinctively pocketed.

Before venturing into Neornithes, the last ornithuran we’ll discuss is Limenavis (Li-men-nay-vis) in which the 70 mya fossil comes from the ‘Allen Formation’ at Salitral Moreno, Argentina. The fossil has been difficult to classify. The remains, definitely of a bird, were originally put down as a basal ornithuran. However, later analyses found it to be much more advanced than Ichthyornis and classified it as a carinate bird (birds possessing a keel or ‘carina’). Thus, as one of the first true birds, scientists gave it the name, Limenavis in meaning, ‘threshold bird’.

Based on the results of the phylogenetic analysis and identification of autapomorphies, Limenavis is now considered to be the closest species to the common ancestor of the crown clade, Neornithes of all living birds. Some paleontologists are even suggesting its anatomical features may put it as a direct common ancestor linked to paleognathes.
Artist: Alexander Lovegrove  Limenavis being flushed
Its distinctive wing bone features, such as the truncate contact of the ulna’s dorsal trochlear surface with the ulnar shaft and the loss of a tubercle adjacent to the tendinous groove on the distal ulna are also found in extant birds. Inhabiting forests along the Atlantic shorelines of Patagonia, it flew about with its wingspan of ~ 43cm/17in wingspan in search of insects, while also in the process of avoiding its much larger dinosaur cousins. Limenavis itself was around 43cm/17.4in long.


Neornithean Cladogram Top: Paleognaths Bttm: Neognaths
Neornitheans are the most recent common ancestors to modern birds including all their descendants extinct and extant. Neornithes is divided into the two superorders: Palaeognathae (Pay-lee-og-nuh-thee) consists of the flightless ratites and the tinamous and Neonagthae (Nee-og-nuh-thee) consists of all other extinct and extant flying birds. The ratites include birds like the ostrich, emu, cassowary, rheas, kiwi, the extinct moa, elephant bird and the extant family, Tinamidae (Tin-ah-me-dee). Tinamous are capable of flight (albeit poor fliers), but are more closely related to ratites, especially in possessing the more primitive reptilian palate in the upper mouth as the ratites have.
Artist: Franco Tempesta  Chicxulub Imoact 
65 mya, Earth was struck by an iridium enriched asteroid/meteorite and along with profuse volcanic activity on the Indian subcontinent in the building of the Himalayas, the events created wholesale catastrophe for established life. The impact also caused coastal/inland damaging tsunamis as evidenced by megatsunami deposits and sediment around and beyond the 161km/100mi Chicxulub crater of the Yucatan Peninsula. This Cretaceous-Paleogene (K-Pg) extinction was another devastating occurrence to life on Earth with 95% of all established marine life vanishing and 70% of all terrestrial life… gone. This includes fauna as well as flora. It ended the reign of all non-avian dinosaurs. The only dinosaurs to escape its wrath were neornitheans.

The Cenozoic Era
The Cenozoic Era, known as ‘new life ’, came after the extinction boundary. It’s divided into three periods as earliest, the Paleogene, then Neogene and Quaternary and lasted just after the asteroid impact boundary 65 mya down to the present.  Even though the K-Pg impact had an effect on global climate along with continental drift playing its part, overall the planet was a continuation of the Mesozoic with tropical to semitropical environments only to begin cooling in the Neogene with resultant ice ages.

No tetrapod weighing over 25kg/55lbs survived beyond the extinction boundary. With bird lineages decreasing in length, this smallness is what most likely aided birds in their survival beyond the extinction boundary.  Able to hide in small burrows, tree holes or shelter in what marsh and wetland environments offered, gave small neornitheans a concealed advantage to extreme exposure limits. Within 10,000 years, neornithean survivors soon after the extinction, dispersed and radiated out filling ecological niches left vacant by those species that went extinct.

Along with birds, 50% of crocodyliforms 80% of Cretaceous turtles, the order Squamata (lizards and snakes), freshwater tetrapods such as amphibians and all the small mammalian lineages except the Asian forms survived through the K-Pg extinction event.

Palaeognathae: Palaeognaths, meaning ‘old jaws’, as just mentioned above is due to the fact that they share a primitive bony palate (mouth roof). Their temporal range is from ~ 100mya at the beginning of the Late Cretaceous to the Holocene of the present. The palate is defined with five unique distinctions and they are:

1)    The large vomer articulates with the premaxillae and the maxillopalatines anteriorly, while the vomer fuses to the ventral surface of the pterygoid with the palatines fusing to the ventral surface of this wholly pterygovomer articulation.
2)    The palatine is also fused into a rigid joint with the pterygoid.
3)    This fusion with the pterygoid prevents the palatine from articulating medially with the basisphenoid.
4)    Articulation on the pterygoid for the basipterygoid process of the basicranium is diverted to the articulation between the pterygoid and quadrate.
5)    The pterygoid/quadrate articulation includes the quadrate’s orbital process.

Palaeognaths also share a similar pelvis anatomy and patterned grooves in the keratinous covering of the beak. For most palaeognaths, the male is the one who incubates the eggs laid down by the female in the nest he arranged. More than one female may lay eggs only in one male’s nest and she may have been fertilized by another male. Only in ostrich species and one species in the genus Apteryx (App-ter-rix), the great spotted kiwi does the female assist the male in incubation. Most palaeognaths have lost their keel.

Except for kiwis’ exceptional brain/body ratios, paleognathes have very small brains compared to body size. Palaeognaths are known for their large sizes with the extant ostrich reaching 2.7m/9ft in length and emus up to 2.3m/7.5ft. But kiwis’ range of sizes is only 36-56cm/14-22in, while the dwarf tinamou is only 15cm/6in in total length. When it comes to mobility, the larger palaeognaths use speed with ostriches capable of reaching 60kph/35mph while the extinct bush moa, with a walking speed of 3-5kph/1.75–3mph, could sprint up to 69kph/43.9mph.

There have as yet been no Cretaceous palaeognath fossil finds, but we do know that the extant five species of kiwis (Apteryx of New Zealand), the three species of cassowaries (Casuarius of northeastern Australia and New Guinea), the emu (Dromaius of Australia), the two species of rheas (Pterocnemia and Rhea of South America) and the ostrich (Struthio of Africa) are all closely related.
Continental Drift
The super continent of Pangea began to split 200 mya during the beginning of the Jurassic into Gondwana and Laurasia. Gondwana gave rise to palaeognath species. 150 mya, at the ending of the Jurassic, Gondwana begins splitting into what would become the continents of Africa, South America, India, Antarctica, and Australia. This splitting dispersed palaeognath species and cut off from their ancient origins began to evolve from environmental isolation. By 140 mya in the Early Cretaceous, Madagascar along with India had split from Antarctica. Madagascar got locked in onto the African continental plate. By 80 mya in the Late Cretaceous, New Zealand had split and drifted from Australia.
Gondwana breakup Griem 2007
Even though there have been no Cretaceous palaeognath fossils yet discovered, with the rifting and breakup creating isolated continents out of Gondwana, it is fair to say that the close palaeognath relationships on each of the segmented continents arose from a common ancestor when these landmasses were one whole landmass conjoined as Gondwana.

However, there is also a controversial analysis that has become the prevailing thought due to its undeniable bare knuckle molecular genetic results. Due to recovered nuclear genome fragments from extinct elephant birds, identified homoplasies (singular: homoplasy ~ independently a gained or lost trait) in morphological traits of palaeognaths and reconstructed morphology based phylogenies, including fossil species evaluations provided stable divergence time estimates enabling a valid argument regarding correlation with geological events.

So, a few researchers have proposed a new evolutionary scenario from this data that contradicts the traditional view. The ancestral Palaeognathae were volant (capable of flight), as estimated from their molecular evolutionary rates and originated during the Late Cretaceous first in the Northern Hemisphere. They migrated aerially to the Southern Hemisphere and explosively speciated around the K-Pg boundary. They then extended their distribution to the Gondwana derived landmasses, such as New Zealand and Madagascar by overseas dispersal. Gigantism subsequently occurred independently on each isolated landmass.

The earliest palaeognath species thus discovered come from the Paleocene and Eocene 61.7-0 mya and are classified under the two families, Lithornithidae (Lith-orn-ah-day) from 61.7-40 mya and Rheidae (Ree-ah-dee) from 56-0 mya, in which rheids are still around today in South America. Also, from ~ 58.7-48.6 mya, Diogenornis (Dye-oge-en-orn-nis) was a stem group casuariiform related to extant cassowaries and emus as well as a sister group to lithornithids.  

Lithornithid fossils come from the Upper Paleocene to the Middle Eocene in what is now North America and Europe. They all were volant (capable of flight), although with long hind limbs and strong tridactyl feet, some were more prone to running before resorting to flight. Lithornithids are distinctive palaeognaths in retaining a fully developed hallux (innermost digit of hind foot, or big toe) unlike their palaeognath descendants whose feet evolved for running speed. Most lithornithids possessed perching feet, well developed keels, pectoral girdle elements and proportionally large wings allowing for soaring flight akin to that of modern birds such as storks.

Once the Pleistocene arrived heralding in the ‘Ice Age’, all the subtropical/tropical climates and environments left the North American continent and with that period change, so too, lithornithids followed suit in becoming extinct.     

There are five genera of lithornithids and they are: Fissuravis (Fis-sure-a-vis) from Germany’s ‘Walbeck’ fissure strata 61.7-58.7 mya; Lithornis (Lith-orn-nis) from Montana’s ‘Bangtail Quarry’ 56-40 mya; Paracathartes (Pair-ah-cath-art-teas) from Wyoming’s ‘Willwood Formation’ ~ 55mya; Pseudocrypturus (Sue-doe-crypt-ur-us) from Wyoming’s Green River Formation’s ‘Fossil Butte Member’ 52mya and Calciavis (Cal-see-a-vis) from Wyoming’s ‘Green River Formation’ 51 mya. The ‘Green River Formation’ of Wyoming is composed of lake bed sediment and is the richest former lake bed for fossils worldwide with its varve layers presenting a continuous six million years record.
Artist: Velizar Simeonovski  Calciavis
Fissuravis is the oldest lithornithid discovered so far and is the only European one as well. Its fossil was found inside a fissure of bedrock filled with sediment debris, thus the source of the generic name. At ~ 40cm/15.8in, Calciavis is the latest species of palaeognath to emerge. Its two fossils, besides bone detail, also revealed exceptional skin, foot scales and feather impressions. It may have coexisted with Pseudocrypturus, but the variance in sizes shows they filled different niches.

Artist: Piotr Gryz  Pseudocrypturus
Pseudocrypturus was ~ 35cm/13.8in long. It had a long narrow beak, long legs and a very short tail, much like the modern day tinamou, hence the generic name in reference to ‘false tinamou ’ and the specific name, cercanaxius (sir-can-ax-e-us) meaning, ‘worthless tail’. Even with a so-called ‘worthless tail’ it could still fly and could perch on tree limbs. However, it likely spent most of its time wading along shorelines foraging for small fish and invertebrates.

Artist: Scott Reid  Paraacathartes
Paracathartes, with a length of ~ 1.1m/3.7ft is the largest lithornithid discovered so far. Multiple fossils have been discovered including one having five individuals and three eggs fossilized together that were covered up and encased in a volcanic explosion’s debris. The egg shells are very ratite-like. Nest sites were also preserved in the fossil site.

Paracathartes was different among the other lithornithids in having shorter and more robust wing elements and a deeper keel relating to a flight style more akin to that of extant tinamous making it far more terrestrial than the other members. With this in mind, Paracathartes could be the intermediate between the other lithornithids and the flightless ratites of today, or it simply is an isolated example of convergent evolution.
Artist: Geraldo  Diogenornis
The Diogenornis fossil comes from the ‘São José de Itaboraí Basin’ of Brazil and after a thorough reevaluation, a study placed it out of the rhea relations replacing it as a stem group to the Australian ratites such as the extant cassowaries and emus. Although it was flightless, it possessed larger wings than do current ratites, but shared in the affinity to run and in possessing narrow beaks. The wings were in a transitional period between its flying ancestors and flightless predecessors. As an herbivore, it utilized the narrow beak in picking off fruits/seeds and slicing leaves, but in supplementing its diet as an insectivore used it in probing for and stirring up insects. It lived in forested habitat making running more ideal than flight for a large bird. Its length was 90cm/3ft. 

As in the extant cassowaries and emus, Diogenornis’ maxilla ended in a point, the tibiotarsus (bird’s leg bone corresponding to the tibia that’s fused at the lower end with some tarsus bones) with the condyles medalis (a rounded articulating protuberance on the inner side of the lower extremity of the femur) aren’t undercut proximally and the shape of the trochlea fibularis (a projection from the lateral side of the calcaneus between the tendons of the peroneus longus and brevis) was large and oval. Along with these shared traits coming from Paleocene South America, Diogenornis’ relations to Australian ratites corroborates a Gondwanan origin of these birds and the close relationship among the Causauriiformes in the extant Rheidae (rheas), Casuariidae (cassowaries), and Dromaiidae (emus) families along with the importance of the Transantarctic biotic interchange of birds between South America and Australia in the beginning of the Cenozoic.

Credit: Izaat Design Lmtd. Moa
Concerning the nine species of moas as endemic to New Zealand, most were hunted to extinction within a hundred years after the arrival of Polynesian settlers (the Māori) 1300-1400 CE. The last more isolated pockets of islander moas became extinct just 600 years ago. The largest, Dinornis, (Dee-nor-nis) reached 3.6m/12ft in total length. Moas were an apex herbivore of the New Zealand islands. The moa temporal range is from 17-0.0006 mya.

Moas, as ratites were flightless, but in addition did not even have vestigial wing remnants as all other ratites did and do. In reproduction, moas laid one 18cm/7in sized egg into a scratched out earthen nest. Laying just one egg and in the addition of studies on the moa cortical bone growth rings, alludes to the fact that moas were K-selected. Species strategies in r/K selection are the concerned modes of successful reproduction utilizing combinations of traits that trade-off between quantity and quality of offspring. In having many offspring with minimal parental care is r-selection. K-selection is in having minimal offspring with much more attended parental care.
Artist: Sameer Prehistorica  Man compared to Moa
As far as diet went, moas feasted upon plant parts including twigs, leaves, fruits, seeds, ferns, mosses and fungi. We know of this due to the analyses of their fossilized gizzard contents and their fossilized coprolites (poop). To aid one in understanding ecological balance, once man had eradicated moas, the beech tree forests started disappearing. Why? Because the fungi spores that were ingested and pooped (excreted) out onto the forest floors by moas, would set up its mycelium underground that dispersed downwards and outwards retaining water and nutrients within the soil’s subsurface. Whenever a natural event occurred like a drought or severe storm that killed off beech stands, the retained water and nutrients gave the beech trees a life line to repopulate in the area that was hit by the disaster. Since man drove the moa to extinction, beech tree stands have dwindled in their radiation throughout the New Zealand islands, which in turn has hampered other life forms that depended on the beech tree forests all simply because of moas being taken out of the chain link to fertilize and spread the forest floors with mushroom spores.

Artist: John Megahan  Haast’s eagle attacking a pair of moas
Also, Earth’s largest eagle, the Haast’s eagle, with females measuring 1.4m/4.7ft in total length while averaging 12.5kg/ 27.6lbs went extinct just after all moas died off. The reason being is that moas were this eagle’s only prey as no other species inhabiting the islands were large enough to sustain the eagle. Until human colonization introduced rodents, feral cats and dogs, the only other placental mammals in New Zealand were three species of bats. Haast’s eagles with strong flight muscles could have reached speeds of 80kph/50mph in surprising and attacking a moa.

Moa foot
Due to the recent extinction of moas, there have been found in caves fossilized remains that still retained soft tissue and bone. The picture above is evidence of a Dinornis foot that was so well preserved DNA could be extracted from it. However, some deviant folk have taken the photo and misrepresented it as a Troodon foot. That is a difference of time in some 60 million years between the two species’ temporal range. The bogus claim went viral for a while, so just be cautious in what you read in internet claims.

Palaeognaths: kiwi, ostrich, moa skeletons
The elephant bird of Madagascar was another huge palaeognath that also went extinct due to man once he arrived on the island. There were three genera in, Aepyornis (Eep-pee-or-nis) Mullerornis (Mule-lur-or-nis) and Vorombe (Vo-rom-be), Perhaps the largest, but most definitely the heaviest bird ever, Vorombe stood 3m/9.9ft tall and weighed 730kg/1,600lbs.
Artist: Brian Choo Elephant Bird (Aepyornis)
Elephant birds, as explained earlier under Palaeognathae did not evolve due to vicariance. Vicariance is the geographical separation of a species population, typically by a physical barrier such as a mountain range or enlarged river, or yes, even continental drift resulting in a pair of closely related species, but no longer same species as the isolated population experiences variant environments from the original population.

According to the mtDNA (mitochondrial DNA) analyses and hybridized enrichment of in-solution RNA arrays of elephant birds, they did not evolve as isolated from an original population during the breakup of Gondwana, but rather via the flight migration of a direct ancestor originating from New Zealand some 50 mya ago well after New Zealand had rifted then drifted from Australia.
Vicariance vs. mtDNA in distribution
In the illustration above, Dr. Kieren Mitchell from the University of Adelaide illustrates his team’s findings as compared to vicariance. Vertical category A displays the breakup timeframe of Gondwana. Vertical category B displays the vicariance phylogenies and vertical category C displays the mtDNA resultant phylogenies. The palaeognaths are color coded the same as the landmass they originated from, so the elephant bird and ostrich are gray as Madagascar and Africa are and the kiwi and emu are red as New Zealand is. From top to bottom in category C, the taxa are moa, tinamou, elephant bird, kiwi, emu, rhea, and ostrich.

Molecular dating uses differences in DNA sequence from one species to another to estimate how long ago the species diverged. This type of technique accounts for genetic changes or mutations that accumulate over a rated time. Thus, the greater the difference in genetic sequence, the farther back the divergence of the speciation dates.

In the illustration below, also from Dr. Mitchell’s team, shows species divergence and phylogenetic position of the elephant bird from the mtDNA sequencing. In mya the blue numbers are the time of divergence. Blue arrows mark the minimum date for the evolution of a flightless lineage as evidenced in fossils and the species description in red are those that are extinct.
Palaeognath genetic positioning
Adding morphological characters to this molecular data set actually increased support for the relationship between elephant birds and kiwis. So, it turns out that the largest ratite, the elephant bird has its closest relation as a sister taxon to the smallest ratite, the kiwi. The elephant bird most likely attained its large size due to insular gigantism from being isolated on an island body and the kiwi obtained smallness in filling a niche by not competing for the ecological niche filled by the moa that had already experienced insular gigantism.
Elephant bird egg compared to a chicken egg
In considering eggs, whether from an extinct or extant animal, it is simply an amazing thing, as an elephant bird egg at 30.5cm/12in long and 71.1cm/28in in circumference is the largest egg thus known, but is almost as large as its closest adult relative, the 40cm/16in long kiwi. The elephant bird egg can hold up to 11L/2.9Gal in volume which is 160 times greater than a chicken egg in equivalency. There are well over 40 elephant birds eggs housed in public facilities and private domains. National Geographic actually has an egg with the embryo fully intact and articulated.

Elephant bird egg compared to an adult kiwi
The vestigial wing bones of an elephant bird follow the classic vertebrate forelimb plan, but displays vestigial flight adaptations in joints modified for folding and locking wings, fused wrist bones and digit reductions. Like kiwis, elephant bird brain endocasts showed reduced optic lobes pointing to a nocturnal existence. This large bird was an herbivore foraging for fruits, especially fruit with endocarps and the coconut palm.

Cast of elephant bird wingbone
New evidence shows that man arrived on the island of Madagascar, 10,000 years ago and initially appeared to coexist with elephant birds. However, there is extensive evidence that these early people hunted, butchered the meat, poached and ate the eggs. δCarbon-13 and δOxygen-18 are stable isotopes found in eggshells. Once analyzed, these stable isotopes in charred elephant bird eggshell fragments can give reference from what topographical region and time zone they came from. Therefore, they can indicate that they were transported from their region of origin to another foreign region.

So, in setting up a biogeographical layout, these charred egg fragments show that the eggs were transported then cooked over a fire. The commonality of these fragment study findings indicates that these early people relied heavily on the eggs, but in coexisting for thousands of years, did not hunt adults that extensively. Perhaps due to a cyclic climate change or a depletion of natural habitat, but not this time solely due to predation by man did the elephant bird go extinct with the last one expiring by the mid-17th century.                            
Current palaeognaths, as ostriches and rheas have long wing feathers that attach to long tridactyl two-clawed hands. Emus and cassowaries have very short wings with a substantially reduced single-clawed carpometacarpus and poorly ossified (fused) splint for the alula. Kiwis have stick-thin wings where the manus (hands) are monodactylous (one digit), elephant birds are the same as kiwis but thicker and of course much larger, while moas had no wings at all.

Of the extant palaeognaths, rheas are the basal most branch. Tinamous and moas share a common ancestor, with kiwis more closely related to emus and cassowaries. Also as previously stated, pretty much the largest bird ever known, the extinct elephant bird of Madagascar has for its closest relative, the smallest extant palaeognath in the kiwi. The sister group to all modern palaeognaths is the ostrich family, Struthionidae (Strut-the-on-ee-dye). The overall direct line to a common ancestor for palaeognaths may go back to 120 mya.

With two extant species, rheas come from South America and have a temporal range of 126 thousand years ago to the present. However, in the family, Rheidae (Ree-ah-dye) there are extinct species and subspecies that go back 56 mya, such as R. fossilis and R. pampeana. Though somewhat smaller, rheas are very similar in appearance to ostriches, their closest relations. 

As a ratite, they are flightless, but use their reduced wings for balance and act as an airfoil for changing direction. The legs are used for running speed in utilizing the legs length and muscle strength. Rheas are omnivorous in dieting on primarily broad-leafed plants, fruit, seeds and roots while complementing the diet with insects like grasshoppers and carrion.

Males are polygamous, mating with two to twelve females and after courtship, builds a nest by scratching a pit in the ground layering it with grass and leaves. The females then lay up to 60 of their fertilized eggs in the nest where the male incubates and tends to the hatchlings. In fending the hatchlings, males will charge at anything he deems threatening to his brood.

There are nine extant genera of tinamou and have a temporal range of 10 mya to the present in quite possibly having lithornithids as being directly ancestral to. The earliest decisive tinamiform fossil found was in Argentinean Patagonia during the Miocene’s Burdigalian Stage 17.5-16.3 mya of the genus, Crypturellus (Krip-tu-rail-us). The extant species come from Mexico, Central and South America.

Like most extant palaeognaths, tinamous are ground birds and as previously stated the male tends to the eggs and hatchlings. But the females lay some unique, fancy and pretty eggs into the male’s nest. Unlike most bird eggs, tinamou eggs are glossy and show hues of vivid color. The reason being is that they are smooth instead of pitted and do not get color from pigmentation, but from iridescence.

Along with the eggshell being made up of calcium carbonate, the last thing the female does prior to laying her egg is coating it with a layer of calcium phosphate giving the egg its smoothness and iridescence. The smoothness gives the glossy appearance and the iridescence gives it the colorful hues. At differing angles, the normal blue color underneath can turn shades of varying colors. No one knows the underlining reason for this tinamou egg attribute, but the ones that did the egg testing and analysis feel that it may aid in attracting females to lay their eggs in a nest with eggs giving off their colorful hues laid previously. With more eggs in a nest, it might be a strategy that more will succeed in hatching due to a lessening of predation if very few eggs were only in a nest.                           

Neognathae: Neognaths possess a differing jaw structure than paleognaths, so the term refers to ‘new jaws’ even though the palaeognath jaw is apomorphic (more derived) between the two and is not indicative to comparative evolution. With over 10,000 extant species, Neognathae covers virtually all living birds from hummingbirds and penguins to vultures and eagles along with their direct common extinct ancestors.
Credit: marysrosaries  Neognath upper jaw vs. Palaeognath
Neognath palatal mobility is due to these three modifications:
1)    Loss of the basipterygoid articulation with the cranium.
2)    A developed process of the pterygoid/palatine joint.
3)    Reduced vomer, or lost entirely doesn’t reach caudally to the pterygoid.   

Molecular dating points to a neornithean Cretaceous radiation where the lack of Cretaceous fossils suggests a Paleocene radiation after the K-Pg extinction. Except for a few near-complete articulated fossils, but mostly a spattering of some isolated bones, there has been some concern sprinkled with a dose of consternation as to why there hasn’t been a trove of Neornithes Cretaceous fossil finds. Neornitheans should’ve been well established at least by 95 mya leading into neognaths.

As has been suggested by paleontolgists, Roger Cooper and Richard A. Fortey, some neorinthean clades did originate deep in the Late Cretaceous but maintained a low Mesozoic diversity. Also, paleo-ornithologist, John L. Cracraft states that the lack of neornithean fossils before the K-Pg extinction event could be the case that much of Cretaceous neornithean evolution took place in the Southern Hemisphere, where the fossil record has been far less thoroughly sampled. For whatever is the reason, I’m quite sure of it that in the not so distant future with more fossil finds and sharp minds, this conundrum will be solved. Anyway, there is fossil evidence of an explosive diversification of modern bird families to fill in the biological niches left vacant after the K-Pg extinction.
Artist: Monica Serrano  Vegavis being chased
Vegavis (Vague-ah-viss), a volant (capable of flight) herbivore just outside the waterfowl crown group of Anseriformes (Ann-sar-uh-for-mees), had a temporal range of 68-66 mya. This 60cm/23.6in long Antarctica bird resembled a duck with long legs and though not directly ancestral, is closely related to modern ducks and geese.

Artist: Nicole Fuller Sayo  Vegavis  syrinx
The fossil find from the ‘López de Bertodano Formation’ was discovered on Vega Island, Antarctica, hence the generic name, Vegavis. But, oh what a fossil find this fossil gem was. In fact, it was of two fossil specimens beside each other. Because of the intricate and fragile nature of the two fossils embedded in a matrix of sediment concretion, 3-D CT scans were performed. Once the scans were evaluated, it revealed in the second fossil a syrinx which is a bird’s vocal organ, equivalent to a human’s larynx. This is a very rare find for the syrinx, composed of very fragile cartilage tissue and mesoderm cells, is rarely fossilized and was still intact in its original position down the neckline along with some large soft tissue.

The syrinx has an asymmetrical third segment to it and with the soft tissue acting as a resonator, suggests that Vegavis was capable of producing deeper toned honks just as ducks and geese do today.
Vegavis scanned syrinx
Where the syrinx is positioned right at the trachea’s Y-junction of the bronchial tubes leading into the lungs, higher up in the throat birds also have a larynx. The syrinx probably evolved to reinforce the split in the trachea, or as most call it, windpipe. Regardless, it evolved into a bird’s major voice box taking over the duties of the larynx and is the single reason birds can produce their songs. No other animal, whether fish, amphibian, reptile or mammal has a syrinx; only the bird evolved one. For this reason, the syrinx is considered an evolutionary novelty.

Birds can also harmoniously sing without interruption in taking a breath, due to their one way entry and exit air passages where there is always a constant flow of fresh oxygenated air. In humans, breathing is much more imperfect. When we exhale and begin to inhale, we actually inhale a bit of the spent exhaled air, contaminating the fresh inflow of oxygenated air. For this and other reasons as dealing with trachea musculature, the human larynx converts only 3% of energy spent into sound where the bird syrinx, as far more efficient, converts 100%.

The advancement witnesses in the Vegavis fossils attest that neognaths were well on their way to modern bird forms before the K-Pg extinction, implying with physical fossilized proof that at least some groups of neognath modern day birds first came from the Cretaceous.   

Genyornis (Gee-nye-or-niss) also belonged to the duck/goose clade of anserimorphs, which mainly represents extinct and extant water fowl. However, at 2m/6.6ft in length and weighing ~230kg/507.1lbs, this was one big goose on steroids. With a temporal range of ~ 126-30±5 kya (thousand years ago) in what is now Australia appears to have simply vanished after 30,000 years.

With vestigial wings, Genyornis was flightless relying on its strong leg muscles and stout hind limbs for rapid mobility. Unrelated to other large flightless birds, Genyornis had a short dentary symphysis and a dorsally directed pterygoid process on the quadrate, a squarish bone that is articulated by the jaws and homologous with the incus bone of the middle ear in mammals. Also, eggshell studies show similarities to megapodes (Australasian land fowl, such as mallee fowl).

With fossils and eggs found in collective sites, Genyornis was social. Studies on Genyornis eggshell fragment piles show that they were heated or cooked on one side going as far back as 47,000 years ago and too, there are ancient aboriginal stone art drawings of Genyornis preserved still today.
Artist: Peter Trusler  Genyornis & Megalania
Genyornis, along with other fauna became extinct pretty much at the same time, which coincides with man’s arrival into Australia some 50,000 years ago. Due to climate change, Australian geographies converted from tree/shrub savannah with occasionally rich grasslands to desert scrub with the interior becoming very arid. As a more specialized herbivore, this put Genyornis in a stressful situation. Already hurting from the ecological pressures, with human predation and poaching eggs, along with man’s systematic burning of grasslands and tree stands, it pushed Genyornis over the edge into extinction. Genyornis also had to contend with Australia’s competitive and predatory megafauna.

Palaeognath ratites weren’t the only large flightless birds, for as in Genyornis, neognaths also had their fair share of big ‘uns…and no, ‘Big Bird’ of Sesame Street fame doesn’t count. Once the reign of dinosaurs were over, other reptiles, mammals and the last of the dinosaurs in birds were now able to fill the void in ecological niches in which for some, gave latitude for size increases.  Below are a few more huge neognaths.
Artist: Jaime Chirinos  Dromornis
Dromornis (Dro-mor-niss) was closely related to Genyornis and also belongs to the water fowl clade of anserimorphs. As well, flightless with stub-like wings, it was larger than its cousin standing at 3m/9.9ft tall. The size rivals that of the elephant bird. Dromornis belongs to an exclusive Australian group of big birds colloquially called ‘Mihirung paringmal’, which is aboriginal meaning, ‘giant bird’. The dubbed common name is, ‘thunder bird’.

The temporal range for Dromornis is 8 mya-30 kya, but the Australian family, Dromornithidae (Dro-mor-nith-ah day) had a temporal range of 25 mya-3 kya. Dromornithids are in the genera, Genyornis, Dromornis, Barawertornis (Bah-rahweir-torn-iss), Bullockornis (Bull-loc-corn-iss) and Ilbandornis (Ill-ban-dorn-iss). The earlier dromornithids were much smaller than the latter as in, Barawertornis having a total length of ~ 1.7m/5.6ft.

In Dromornis, the species was dimorphic with the males more robust, stout and heavier than the females, but both sexes were much the same size in length. With the huge and powerful beak, some earlier research statements inferred that Dromornis was a carnivore, however later analyses proved the beak lacked carnivory features while showing features favorable to an herbivory diet. This bird was indeed a generalist herbivore eating fruit, nuts, various plant foliage and roots.
Artist: Taringa  Gastornis
Gastornis (Gas-tor-niss) was dispersed almost worldwide with fossils being found in western-central Europe, North America and Eastern Asia with a temporal range of 56-45 mya. It had a length of 1.8m/6ft and weighed around 90.7kg/200lbs. Its extinction after 45 million years ago is suspected to be due to global climate warming and stiff resource competition from growing mammalian populations. It was also an anserimorph.  

Gastornis skeletal
Gastornis fossil remains were first discovered in France in 1855. Meanwhile, a couple decades later, Diatryma (Die-ah-tree-mah) fossil remains were unearthed in New Mexico, USA. Now let’s remember, back then and with a big pond between the two nations called the Atlantic Ocean, there was no rapid communication in the WWW, even on radio or TV, so both generic names stuck as implying that both Gastornis and Diatryma were distinct species. However, as early as 1884, through writings and observation comparisons of the remains, obvious similarities were beginning to be noted and by 1980 after more fossils had been found and closely evaluated, there was so similar a degree in anatomical form that it was decided to drop the genus, Diatryma, and use the genus, Gastornis since it was the one first discovered. There is still articles out there on Diatryma, so just remember that Gastornis and Diatryma are one and the same.

Another snag in Gastornis is that again, since it was big with a huge powerful beak, initially it was thought it must have been carnivorous going around the forests chasing down little mammals and gobbling them up. But, a carnivory biochemical jaw analysis did not pan out as so and Gastornis possessed an herbivore foot with no carnivore claws, while calcium isotope studies of its bones show no evidence of it in being a meat eater.

The eggs of Gastornis were unique in that instead of being round or even oval, they were oblong and measured 25.4cm/10in long by 10.2cm/4in in diameter. Besides the numerous anatomical fossil remains, also discovered have been its feathers from a ‘Green River Formation’ fossil find and footprints from France and Washington State, USA.
Credit:  Phorusrhacos
Known as the ‘terror bird’, Phorusrhacos (Foe-roos-ray-cuss) is related to the extant seriemas, falcons, parrots and passerines of the order, Cariamiformes (Kah-rye-am-uh-forms). As an apex predator of Cenozoic South America from Patagonia 12 mya, Phorusrhacos truly was a huge bird carnivore. Coming from Argentina’s strata of the ‘Santa Cruz Formation’, this bird was 2.5m/8.2ft long and weighed ~ 130kg/290lb.

Phorusrhacos, with greatly reduced wings was flightless and stood on long stilted-like legs looking somewhat like an extant red-legged seriema with a huge beak. Its vestigial wings had the forelimbs manus ending in a hooked claw. Ya might note that the generic name doesn’t end in ‘ornis’, which is Greek for ‘bird’, as most other large flightless neognaths do. That is because the first Phorusrhacos fossil discovery in 1887 consisted only of a partial lower jawbone and was mistakenly identified as coming from a mammal. That was soon corrected in 1891 after more fossil finds collaborated in what the jawbone really came from, but the generic naming stuck.
Phorusrhacos skull
With the weaponry Phorusrhacos had, there was a number or combination of ways it would take down its prey. In hunting down smaller mammals and reptiles, one way is in utilizing the pointed and hooked beak as it chased larger prey, it could easily stab through the head entering the brain or the cervical vertebrae snapping the neck instantly in bringing down its victim. For neutralizing smaller prey, just as extant seriemas do today, Phorusrhacos may have picked up the prey and slammed it down on the ground in a repeated process. This would also be beneficial in tenderizing the prey in smushing the meat and breaking bone.

But with mid-size to smaller prey, I would like to include that Phorusrhacos, with its long legs may have pounced onto the prey and while bearing down, with its weight sinking claws into flesh, pinned the prey securely to give it a few shots with the pointed tipped beak. This is how the extant secretary bird catches its snake prey and with the long legs in both birds, it keeps the body away from the dangers of a struggling or defensive prey. Phorusrhacos most likely would not have passed up the opportunity to scavenge any carrion it came by either.

Nonetheless, the wings’ hooked claws would not have been too much of an advantage in seizing prey as it would’ve brought the head and torso too close to a defensive prey’s retaliation. The wings’ hooked claws if used at all would’ve been for combating a fellow competitor during mating or territorial rights.
Artist: Jaime Chirinos  Titanis
There was later other fossil finds in what is now Florida and Texas, USA that had very similar anatomical features as Phorusrhacos, but given their latter temporal range of 5-2 mya, a more robust/stout legs and body while possessing two wing claws instead of the one long hooked claw, it was designated a new genus as, Titanis (Tye-tan-nis).

In fact there followed many other fossil finds that closely resembled Phorusrhacos, but with a few distinguishing features it soon was revealed the super family, Phorusrhacoidea (Foe-roos-ray-koi-dee-ah) was needed and devised. With 18 genera of ‘terror birds’, below is the member listing under the superfamily, Phorusrhacoidea:
Credit: Manasataramgini  Terror Birds 

Superfamily: Phorusrhacoidea
Genus: Lavocatavis – Middle Eocene Glib Zegdou Formation of Algeria

Family: Phorusrhacidae
Genus: Patagorhacos – Early Miocene Chichinales Formation of Rio Negro Province, Argentina.

Subfamily: Brontornithinae — species standing over 2.3m/7.5ft high. Some monophyly placement dispute in Phorusrhacidae
Genus: Brontornis [Early to Middle Miocene (Santacrucian-Laventan) Santa Cruz and Monte León Formations, Argentina]
Genus: Paraphysornis [Late Oligocene to Early Miocene (Deseadan) Tremembé Formation of São Paulo State, Brazil]
Genus: Physornis [Middle to Late Oligocene (Deseadan) Sarmiento Formation of Santa Cruz Province, Argentina]

Subfamily: Phorusrhacinae  — species 3.3m/9.9ft high, but somewhat slender and decidedly nimble
Genus: Devincenzia [Late Oligocene to Early Miocene (Deseadan) Fray Bentos Formation of Uruguay]
Genus: Kelenken [Middle Miocene (Colloncuran) Collón Cura Formation of Río Negro Province, Argentina; largest known phorusrhacid]
Genus: Phorusrhacos [Early to Middle Miocene (Santacrucian) Santa Cruz Formation of Argentina)
Genus: Titanis [Early Pliocene to Early Pleistocene (Blancan) of Florida/Texas]

Subfamily: Patagornithinae — intermediate sized/very nimble species, standing ~1.7m/5.6ft
Genus: Patagornis [Early to Middle Miocene (Santacrucian-Laventan) Santa Cruz Formation of Santa Cruz Province, Argentina] – includes Morenomerceraria, Palaeociconia, Tolmodus
Genus: Andrewsornis [Middle to Late Oligocene (Deseadan) Agua de la Piedra Formation of southern Argentina]
Genus: Andalgalornis [Late Miocene to Early Pliocene (Huayquerian) Ituzaingó Formation of northwestern Argentina]

Subfamily: Psilopterinae  — species standing 70–100cm/2.3–3.3ft
Genus: Eleutherornis [Middle Eocene (Bartonian) of Rhône, France and Baselland, Switzerland]
Genus: Paleopsilopterus [Middle Paleocene (Itaboraian) Itaboraí Formation of Itaboraí, Brazil; identity as a phorusrhacid dubious]
Genus: Procariama [Late Miocene to Early Pliocene (Huayquerian-Montehermosan) Cerro Azul and Andalhuala Formations of Catamarca Province, Argentina]
Genus: Psilopterus [Middle Oligocene (Deseadan) Santa Cruz Formation and Late Miocene (Chasicoan) Arroyo Chasicó Formation of southern and eastern Argentina]

Subfamily: Mesembriornithinae   medium-sized species standing 1.2-1.5m/ 3.9-4.9ft
Genus: Mesembriornis [Late Miocene to Late Pliocene (Montehermosan) Monte Hermoso Formation of Argentina]
Genus: Llallawavis [Late Pliocene (Chapadmalalan) Playa Los Lobos Allo Formation of northeastern Argentina]        

Below is a documentary on South American ‘terror birds’. At nearly fifty minutes it is a bit lengthy, but if ya have time, it’s well worth it:

With a temporal range of 58.7-2.5 mya, the family, Pelagornithidae (Pal-ah-gor-nith-ah-day) consisted of seabirds dispersed all over the Late Paleocene-Early Pleistocene world. Fossils have been found in coastal rock from Belgium through Togo to Antarctica. Also known as false-toothed birds, pelagornithids had pointed tooth-like projections jutting from the edges of the beaks. Unlike true teeth and more like bone, these beak teeth contained Volkmann’s canals that are micro channeled tubular arrangements interconnecting haversian canals to one another. These tooth-like points were outgrowths of the premaxillary and mandibular bones.
Artist: Mark Witton P. chilensis
From the smallest pelagornithid, Odontoptila (O-don-top-till-ah) at about the size of today’s white-chinned petrel in having a wingspan of ~1.5m/4.6ft, to the largest pelagornithid, Pelagornis sandersi (Pail-ah-gor-nee = san-der-see) with a wingspan of 6.1-7.4m/20-24ft, pelagornithids were the largest birds to ever fly.

Artist: Jose Vega a pelagornithid
To have such a large size and still get by in overcoming gravitational pull for liftoff to fly while remaining airborne, pelagornithids employed two strategies in anatomy and aerodynamics. Pelagornithids, in dropping body mass possessed extremely thin-walled bones that were extensively pneumatized with air sacs leading to the lungs. This allowed the birds to remain below critical wing loading which is 25kg/m2-5lb/ft2 for powered bird wing flight. In addition, pelagornithids in utilizing attachment positions for muscles responsible in holding the upper arm straight and outstretched were well-developed and they also had a glenoid joint unmatched by any other bird in holding the wings rigid. While less developed in older Paleogene forms, this was especially prominent in Neogene pelagornithids. This anatomical arrangement allowed pelagornithids to successfully practice dynamic soaring, which is a flying technique used to gain energy by repeatedly crossing the boundary between air masses of significantly different velocity. Dynamic soaring is explained in the video below.

P. miocaenus skeletal
There have been several hypotheses presented on what the reasoning(s) were for the extinction of this successful bird’s reign. From over competition with newer oceanic species, such as the radiation of pinnipeds (seals) and cetaceans (whales) to loss of breeding grounds to predation and habitat destruction due to rising oceanic waters are some. But most recent studies reveal a negative ecological change in the ice age commencement and plate tectonic shifts changing ocean currents that created the colder Antarctic circumpolar current and closed the Isthmus of Panama that most likely had the greatest impact over the demise of pelagornithids in failing to adapt. Also, primitive dolphins of the family, Kentriodontidae (Ken-tree-ah-don-tuh-day) or the shark-toothed whales of the family, Squalodontidae (Squaw-lo-don-tuh-day) with similar pelagornithid oceanic feeding patterns, flourished contemporaneously with the pelagornithids, but became extinct around the same time.

As mentioned earlier above, P. sandersi belonged to the family of birds with the longest wingspans ever, while at, 6.1-7.4m/20-24ft it had the largest wingspan of any pelagornithid yet discovered. As in all pelagornithids, its false-teeth weren’t composed of enamel or any other hardened material, so were fragile as numerous fossils attest to in broken pseudo teeth. This alludes to the fact that food had to be soft-bodied like cephalopods or scaleless small fish. This would make good in utilizing the pseudo teeth for snatching prey just below the surface and swallowing whole, but not for tearing or chewing prey. As in being related to pelicans, a pelagornithid’s mouth was mechanized to open wide. Inside the eye sockets of some pelagornithid fossils, salt glands were evident, in particular in younger ones.

P. sandersi lived during the Oligocene 25 mya off the coast of what is now South Carolina, USA. It had short stumpy legs ending in webbed feet with no hallux (big toe) and most likely hopped towards a cliff whenever it was ready to take-off and become airborne. In performing dynamic soaring, it has been estimated that it could reach speeds up to 70kph/37mph and filled the oceanic niche that pteranodons had left vacant.          

In the direction of rooted phylogenetics, basal penguins first show up as the most recent common ancestor 70-68 mya, a few million years before the K-Pg extinction. This occurred within the regions of what is now southern New Zealand and Byrd Land, Antarctica. Penguins didn’t come directly from flying birds, but their basal ancestral flightless seabirds did.

As wing propelled divers, by 60 mya penguins were already adapted to a marine life. Further, through molecular genome studies, a descendant of the basal penguin, designated as ‘Penguin One’ gave rise to all modern penguins. Somewhere around 40 mya, ‘Penguin A’ evolved giving rise to the giant penguins in the genus, Aptenodytes (App-ten-o-dye-tees), which includes the two extant species, the Emperor and King penguins. This ‘A ’genus split off from a branch that lead to all other latter penguin species. ‘Penguin B’~ 37.8 mya gives rise to the genus, Pygoscelis (Pee-goss-sul-lis), which includes the three extant brush-tailed penguin species. Mitochondrial and nuclear DNA bears out the fact that ‘Penguin C’ from ~ 25 mya gave rise to the genus, Sphenicus (Suh-fin-cuss) that in turn gave rise to penguins closer to the equator in the four extant species, the African, Galápagos, Humboldt and Magellanic penguins. The cold oceanic currents, such as the Humboldt and Cromwell allow the Sphenicus species to survive, in which their ancestors traveled up into.  Finally, ~ 5.35 mya a direct ancestor for the genus, Eudyptes (U-dip-tees), gave rise to the extant seven species of crested penguins.
Credit: Hedwig Reunes-Vanhaevre

Since they were now an oceanic bird, basal penguins had begun the process of devolving back to heavier bones filled with marrow. Thinner bones with air filled cavities for flight advantages were no longer viable for a watery environment, but added weight for submergence and countering buoyancy was.

The earliest penguin fossil finds combines primitive and derived characters.  Incorporating fossil calibration points, DNA sequences, maximum likelihood, and Bayesian analysis, penguin calibrations imply a radiation of modern (crown group) birds in the Late Cretaceous 74 ± 3 mya.
Some prehistoric penguins
Ancestral penguins survived the K-Pg extinction event that killed off the big, non-avialan dinosaurs and then rapidly blew up in body size. Quite possibly, this rapid evolution and diversification in the southern oceans was in response to the sudden demise of large marine reptiles, which initiated an ecological vacant niche that large penguins obliged in filling that role.

Credit: Slack et al Waimanu tuatahi
Waimanu (We-mah-nuh), occurring 60 mya was one of the more transitional primitive penguins. Discovered in New Zealand’s ‘Kokoamu Greensand’, two species of Waimanu in, W. manneringi (1m/ 3.4ft tall) and W. tuatahi (80cm/30in tall) have been found and studied. Rather than a stubbier modern penguin beak, the Waimanu species had a long narrow pointed beak. Shorter than a modern bird’s wing when compared to body size, Waimanu’s flipper as equivalent to a wing was significantly longer relative to the body than today’s extant penguins’ flipper. It also could fold in the two wrists and elbow joints. However, the flipper bones had already been transitioning into the flattened anatomy, but not as quite as they are in extant penguins. The hind limb bones indicate an upright posture like extant penguins employ. The feet were short and stubby, but unlike the characteristic waddle of the penguin gait, Waimanu was more of a cormorant stride.   

Icadyptes (I-kaah-diptz) occurring in what is now Peru from the coastal desert marine rocks of the, ‘Otuma Formation’ lived ~ 36 mya and was around 1.5m/4.9ft in length. It is the ancestral apex sphenisciform in beak length possessing one that reached 20cm/8in long. Still possessing the basal ancestral long pointed beak, Icadyptes’ beak was exceptionally long and is known as the spear-like beak penguin.
Icadyptes beak comparison
Peru 36 mya had a tropical climate with warm seas. With Icadyptes already established there during that time, shows that penguins had already adapted to warm climates by 40 mya. The hyper elongate spear-like beak was held by a narrow skull affixed to a robust cervical column. Unlike the thick rugose rhamphotheca (thin horny sheath composed of modified scales of a bird’s bill) of extant penguins, Icadyptes’ beak had a thin, sheet-like rhamphotheca lamination.          

Palaeeudyptinae (Pay-lee-oi-dip-sha-nee), fossils found from the Middle/Late Eocene to the Middle Miocene is an extinct penguin sub-family group that had some of the largest penguin members to ever swim the oceans. The fossils were discovered in what is now: Antarctica, Australia, New Zealand and the western side of South America. The decline and eventual extinction of Palaeeudyptinae species coincides with the competing forces of cetacean and pinniped mammal groups and in addition, the coming of colder climates and ice.

As a mid-evolutionary lineage Palaeeudyptinae species were more primitive than today’s penguins in transitioning modern characteristics but still retaining anatomical features from their seabird ancestors. While ancestral wing feathering had already been lost, the semi-rigid flipper assemblage had not occurred as in today’s penguins. For propelling capacity while diving, the ulna (long bone in forearm) and radius (shorter bone in forearm) had already flattened for increased capacity. The elbow and wrist joints however, still retained degrees of flexibility as opposed to the rigidly locked joint mechanisms in extant penguins.
Artist: Discott
Two genera belonging to the subfamily, Palaeeudyptinae were Anthhropornis (An-throp-or-niss) and Pachydyptes (Pac-he-dip-tees). Thus far, the discovery of Anthhropornis details the largest penguin ever to swim the seas. At 1.8m/5.9ft, it was huge and for comparison, today’s largest penguin, the emperor stands at 1.2m/3.9ft tall. Since they were almost 1.9m/6ft tall the genus name refers to, ‘man-sized bird’. A characteristic feature held onto is inherited from its flying bird ancestry in having a bent wing folded by a ligament. There are two species in, A. nordenskjoldi as being slightly the larger and A. grandis. The fossils were discovered off the coast of Antarctica on Seymour Island from the ‘La Meseta Formation’ and in New Zealand.

Where Anthhropornis was close to being as long as a VW Beetle automobile, Pachydyptes (Pac-he-dip-tees) was about as wide as one. This penguin was massive in girth with a weight of up to 100kg/220.5lbs, but a height of only 1.5m/5ft. This is not conclusive as the mass was calculated by only a few bones contained in the fossil find, but experts in reconstructing fossils agree that the estimate is close if not accurate. It’s not just from the bone sizes in determining the weight, but also in the wing bones, the width shows signs of being extremely stocky in girth. The wing bones are 35% longer than and nearly twice as thick as an emperor penguin’s.

We’ve gone over a lot of giant penguins, but in the tiny Eretiscus fossil from 22 mya of Patagonia, Argentina, there was room for some small penguin niches as well. Originally named Microdytes in meaning, ‘tiny diver’ but named changed after it was found that a water beetle had already been given that genus name. The current and now permanent name change is, Eretiscus in meaning, ‘tiny rower’. We’re only talking about millimeters here, or one-fortieth in inches difference, but this penguin is around the size of the extant blue penguin at 46cm/18.1in and 1.5kg/3.3lbs in weight so, it may or may not be the smallest penguin ever known, but it is currently the smallest penguin fossil ever known.
The Blue Penguin
Although the colder Pleistocene climates and glacier advances may have contributed to primitive penguin species extinctions who evolved in warm climes, the peaking of glacial advance-retreat cycles in the Pleistocene appear to have been a driver of extant penguin evolution. According to a 2017 Bayesian study combining fossil and extant species data, the results show that 12 of the 18 living species likely arose just in the last 2 million years.

To answer the question, “Do penguins have knees?”…yes they do; in fact the structural penguin leg configuration is the same as that of a human leg consisting of a femur, tibia and fibula. However, the femur is short and points outwards and upwards before joining the tibia and fibula at the knee joint. With this configuration, it’s like a human walking on stilts. Also, with the knee joint up so high, there is an illusion developed by fur covering and hiding the joint and most of the leg making the legs look very short and the gait appear as stiff legged.
The penguin knee
In fact, this same characteristic penguin waddle has been found in a yet unnamed new penguin fossil discovery that comes from New Zealand’s ‘Waipara Greensand Formation’ from sediment rock that is 61 million years old. At 1.5m/5ft in total length, this penguin was large and shows the fact that penguins were enlarging early on in their evolutionary history pushing back its diversity well before the K-Pg extinction. This Waipara penguin fossil had already evolved flattened flipper (wing) limbs much like modern penguins displaying a morphology much more derived than Waimanu.

The 61 mya penguin foot versus extant emperor penguin
From their basal ancestors, extant penguins inherited the ability to navigate the oceans by the sun’s location and recognizing landmark features of coastlines and the ocean bottoms.

A hoatzin pair
Hoatzin species were once widespread and were found in Europe and Africa as well as one species currently still living in South America confined along the Amazon drainage basin and the Ornico. The current species is the only extant member in the family Opisthocomidae (O-piss-tho-calm-i-die). With an oversized crop used for fermentation, the hoatzin is a folivore subsisting on leaves, but may complement the diet with flower petals and fruit.

The oldest known fossils come from Europe near Romainville, France. The fossil was found in sediment that was deposited at the very end of the Eocene 34 mya. The genus name is Protoazin (Pro-toe-ah-seen). Namibiavis (Nuh-mib-e-a-viss) comes from what is now Namibia, Africa and was found in Middle Miocene deposits laid down 16 mya. Genetic research alludes to the fact that the hoatzin is the last surviving member of a bird line that branched off in a separate direction from the rest of bird lines 64 mya and dispersed throughout the world.

Hoatzins do not fly well, so for those who argue that opisthocomids evolved in one land and flew over vast oceans to populate different lands will have a problem. In my opinion, hoatzins dispersed early on when continents and land bridges were much closer and not later on in the Cenozoic when huge oceans separated the current continental distributions.
Hoatzin chick with forelimb claws
Hoatzin chicks have functional claws on the second and third digits but lose them as they mature into adults. The forelimb claws in conjunction with the hind limb claws are used by the chicks to clamber over the thick branches when seeking shelter or to escape predation. Also, hoatzin nests are usually over a body of water and if necessary, a chick will drop into the water body and swim submerged to escape any danger. Musculoskeletal remodeling of forelimbs in hoatzins incorporates functional consequences of changing morphology by manipulating anatomical parameters. Due to the chicks requiring a variance of climbing techniques and swimming over flight, once matured, the hoatzin is a poor flier. As well though, the crop is so large that it has displaced flight muscles and keel size.

A horned screamer’s claws
Hoatzin chicks are the most well-known birds to have forelimb claws, but there are other extant birds with their young bearing claws, such as the turaco while the horned screamer retains two spurred claws on each wing throughout life. These are cases of switching on the theropodal gene for forelimb claws due to secondary adaptations. But when a bird that usually never has claws then one individual of a species does, say like a duck, then that is a true mutation.

A duck with forelimb claws
Although it has been expounded on in modified terms throughout the millions of years, birds and mammals both inherited the reptile brain. One might think that birds and humans are so vastly different and that may be so anatomically, but when it comes to brain power…evolution, no matter how distant the ancestor, both human and bird shared a common archosaurian predecessor that gave us similar mental components of the brain to think, react, experience emotive forces and simply to just have fun.

It is true that in the developing embryo of a bird and human, the pallium (layers of grey and white matter covering the upper surface of the cerebrum in vertebrates) in birds is derived from the lower surface of the roof of the fetal forebrain, while in mammals, including humans, the neocortex is derived from the developing fetal brain’s upper surface. That is an extrapolation of convergent evolution and not associated gene evolution. The neocortex along with the archicortex and paleocortex, in which all three are cortical parts of the cerebral cortex, are involved in higher functions such as sensory perception, generation of motor commands, spatial reasoning, conscious thought, and vocally lingual communication.

However, in birds and mammals and again, this includes humans, the same genes are responsible for the proteins in the developing embryonic forebrain that produce the proliferation and arrangement of neurons. It just so happens that this occurs on the lower surface of the pallium in birds and on the upper surface with mammals.
Artist: Tony Angell a crow’s brain 
Although the bird pallium of the forebrain is three layered into a hyperpallium, the neural connections are distributed in patchy centers rather than layers in devising environmental perceptions. Wherein the mammal’s neocortex connections only consist of six layers of intricate neural cell interconnections with no networking patches in perceiving the surrounding world. But, the patchy hyperpallium of the bird’s forebrain is homologous to the mammal’s layered neocortex as both were derived then springboarded from the ancestral upper surface of a reptile’s embryonic brain. The result; both function the same in the accessing, integrating, interpreting and resultant action in the flood of information coming from their environment.

In thinking, requisitions required for the brain to interpret and interpolate are the chemical messages, the electrical pathways and the mechanical apertures to produce them. Both the bird brain and mammalian brain utilize the same genes, neural electrical transmitters, enzymes and hormones as messenger carriers such as adrenalin, corticosterone, dopamine, opioids and the FoxP2 gene that is critical to stimulating nerve development and connectivity in social animals for language and song learning. Just as in humans, birds can reconsider sensory information by rewiring neural circuits that loop between the thalamus and pallium.
Artist: Tony Angell neural looping
Just as in most humans, in most birds, socialization is critical for the species as a whole. Play is an important action in social animals as a means to learning, exercise and relief of stressful tension. Chickens, cranes, cuckoos, ducks, gulls, hawks, hornbills, owls, parrots, pigeons, songbirds, swifts and even woodpeckers all play. However, I will only dwell a bit on the social behaviors of corvids, the family of crows, ravens, magpies and jays, but in particular on crows and ravens.

Wild crows play and play a lot, even adults. It appears to bolster their insight as a motivation to explore, solve problems, assess situations, sharpen their ability to think of the past to plan for the future, or simply to frolic.

In Washington State, crows were seen flying in formation on a cold winter day only to break formation and dive bomb to the top of a water tower where warm air was rising from it. As the warm air rose, the crows would spread their wings allowing the rising warm air currents to glide them upwards until the rising warm air was saturated enough with the surrounding cold air that it would no longer support any more lift. From there the crows dove back down repeatedly to the top of the tower to rise but once again.

A crow at play will pick up a stick and poke another with it, until the one being poked grabs the stick away from the poker, switching roles in turning the poked into the poker. On the tips of branches or wires tied to branches, crows have been seen grabbing the branches and wires with their beaks or feet then head knob until they begin bouncing up and down. Ravens have been seen bobsledding down snowy hillsides either on their backs or belly and once down the hill fly back up to do it again.
Artist: Tony Angell Ravens wind surfing
A favorite game of raven play in Colorado’s Rocky National Park is to surf the wind when strong winds slam into a cliff or mountainside causing updrafts. Ravens have been witnessed by human crowds in picking up a thin sheet of bark with their feet then flying towards the top of the cliff or mountain they enter into the updraft and wind surf down through it. They will do this for hours on end.

These forms of play activity builds, re-circuits and refines synapses in the bird’s brain developing required social skills. This neurobiology of play, as in mammals rewards brain circuits with new chemistries. Important regions of the social brain affect certain sections of the forebrain such as the amygdala, which acquires and retains memories sorting out the pleasant from unpleasant emotional experiences and the septum which integrates the information from those memories and the hippocampus that affects social bonding.

As far as emotional sympathy or even sadness goes, the bird’s brain can also analyze situations calling for these symptoms. Harpy eagles of Brazil are monogamous and mate for life. When one loses a mate, they will mourn by incessantly crying out in screeching. While back to crows, these birds have been seen lining up to view a fallen associate as the victim of car hit. It’s almost like in a human’s funeral, where congregants line up to view the deceased at a funeral for the last time. Crows have even been seen helping an injured crow move by two other crows holding the injured one up from both sides.    

By no means did I go over all the extinct bird-like and bird fossils. To see a more detailed listing, click on the link below:

In Summation:
So, down through the Archosauromorph line from crocodilians through dinosaurs and finally, to birds we’ve covered this evolution through the study of fossils.
Fossils reveal that dinosaurs originated in what is now South America, and geologically soon afterwards first diverged into sauropodomorphs, then ornithischians and theropods before dispersing across the Triassic world more than 220 million years ago.

Fossils reveal a lot; much more so than as simply a species identifier. Youth variations versus adults, what they ate, whether they chewed or swallowed food whole, how they digested what they ate, body coverings in skin, scales and feathering, environmental conditions they existed in, temperature ranges and how they nested; all are revealed in fossils.

T. rex jaws infected by trichomonas (arrows) 
Even diseases and wounds are determined in what the dinosaur went through from infections to arthritis to broken bones and wounds. Activity-related bone fractures have been documented in ceratopsians. Periostitis (inflammation of periosteum tissue that surrounds bones) has also been documented in the shoulder blade of a ceratopsian. Triceratops horn healing and rejuvenating after being injured from an earlier T. rex attack attests to this evidence. Also in the basal plesiosaur, Lagenanectes, the basioccipital (bone in the base of the cranium) and atlas intercentrum (forming the connection of the vertebral column with the skull) are pathologically deformed due to an osteomyelitis infection.
Artist Chris Glen T. rex with trichomonas
A T. rex skull fossil shows structurally different holes bored through the jaw and skull. These are not tooth puncture wounds and appear to be holes bored by a parasite and in particular the parasite, Trichomonas that affects birds today.   

Artist: Jan-Ake Winqvist Maiasaura
Fossils also give us a window to peer into dinosaur parental care. ‘Two Medicine Formation’s Egg Mountain in northern Montana displays parental care in a nesting colony site of the dinosaur, Maiasaura (My-uh-sawr-uh). Numerous nest sites, eggs and young were found. The eggs were arranged in dug out earthen nests that were an adult’s body length in distance from each other. The baby fossils displayed skeletons that still were composed of more cartilaginous material than bone tissue, too much so that they could not yet walk. This alludes to the fact of altricial conditions, so parental care would’ve been necessary for young survival. Also, in the different stages of the baby and young ages, Maiasaura youth grew extremely fast as comparable to bird hatchlings and fledglings.  

Of course fossils give details of anatomical structuring. The dinosaur vertebral column consists of the cervical (neck), dorsal (back), sacral (hips), and caudal (tail) vertebrae. Saurischian fossils tell us that dinosaur vertebrae sometimes possessed features known as pleurocoels (hollow depressions on the lateral portions of the vertebrae) that are perforated creating an entrance into the air chambers within the vertebrae, serving the dinosaur in decreased bone weight without sacrificing strength. Pleurocoels were filled with air sacs in furthering weight deduction.
Pneumatic pleurocels

As the largest known land vertebrates, sauropod dinosaurs’ pleurocoels and air sacs may have reduced the animal’s weight by over a ton, a handy evolutionary adaption in animals that grew to over 30 meters in length. In many hadrosaur and theropod dinosaurs, the caudal vertebrae were reinforced by ossified tendons.

Going all the way back to the avialans 125 mya, Sapeornis lacked teeth as an adult in the lower jaw, while Jeholornis was in the process of reducing teeth; changing the typical dinosaur snout into an atypical bird beak.

Latter enantiornitheans were trending towards stronger flight just like the euornithean progenitors of modern birds. Through convergent evolution, the enantiornithean, Mirarce (Mir-r-say), though totally separate from the euornithean line of modern birds had evolved highly refined adaptations for advanced flight.

The fossil of Mirarce shows it still retained more primitive enantiornithean anatomical features, but also had evolved a more deeply keeled sternum for stronger flight muscles to attach to and unlike its enantiornithean relatives in possessing a U-shaped furcula (wishbone), its furcula was more V-shaped as in euornitheans and modern birds. However, by the time the K-Pg extinction came, all enantiornitheans had become extinct, even Mirarce who lived 76-74.1 mya.
Artist: Brian Engh Mirarce atop Utahceratops
Once you put all that is known of vertebrate fossils, it becomes a page-by-page book with chapters leading into the next building up a story through time in how little-by-little, bit-by-bit one ancestral extinct animal evolved into a more modern one due to evidenced environmental change and natural selection pressures.   

The most costly mobility expense in energy is flight. We just touched base, but it is truly an exciting event in seeing how ornithuromorph fossils had already provided the pathway for modern birds to inherit a specialized digestive system that is lightweight, efficient and capable of sustaining the energetic demands of powered flight.

The most unique inherited feature of birds is in having feathers that enabled flight, provides insulation, camouflage protection and visual communication. Modified feathers aid in swimming, sound production, water repellence, tactile sensation, hearing, and body support. Theropdal adaptations for flight include fusion and reinforcement of lightweight bones and the presence of a keeled sternum in supporting flight muscles, homeothermy (warm-bloodededness), produce external eggs, and demonstrate complex parental and reproductive behaviors. Other reptilian and most likely theropodal shared features include nucleated red blood cells, a single middle ear bone, and a single occipital condyle on the back of the skull. Birds uniquely possess vocalization usage to mediate social interactions, have distinctive bills/feet and are able to detect and react to magnetism.  
Credit: Ikononet. com Distinctive bird beaks and feet
In ‘Et Tunc Nulla Erat VII’, from large toads to pterosaurs to even early day mammals, we mentioned how dinosaurs were preyed upon by other animals, but dinosaurs surely had other animals, besides other dinosaurs on their menu lists as well, as is the case in the picture below.
Artist: Luis V. Rey Carcharodontosaurs/Ornithocheirus
I’ll leave you with Spain’s 129.4-126.3 million-year-old ‘La Huérguina Formation’s newly 2018 discovered fossil of a recently hatched juvenile enantiornithean. Due to the fossil’s exceptional detail, researchers know it was an enantiornithean, but due to its very recent discovery, have not as yet assigned it to a genus or species nomenclature.

The enantiornithean hatchling
For those that still don’t think birds came from dinosaurs…have ya ever stared back into the eyes a shoebill stork…

The Shoebill Stork
For the next ‘Et Tunc Nulla Erat’ series, we’re gonna go back in time, revisit and pick up the synapsids that eventually lead to mammals.

Happy Birding