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|
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|
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.
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.
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|
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.
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 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.
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|
|Artist: Zhao Chuang Caihong|
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|
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.
|Artist: Emily Willoughby Eosinopteryx|
|Anchiornis wing fossil with skin (white)|
|Artist: Zhao Chuang Anchiornis|
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|
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|
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|
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|
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.
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|
|Artist: Jaime Chirinos Confuciusornis feducciai|
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 fossil toe scales|
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|
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.
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.
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|
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|
|A. Protopteryx B. Eoenantiornis|
|Sculptors: José Manuel & Benito Álvarez Iberomesornis|
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|
|Artist: Jack Wood Lianoningornis|
|Artist: Jack Wood Eoenantiornis|
|Artist: Danneart Sinornis|
|Artist: Leau Bellon Cathayornis|
|Artist: Scott Reid Eocathayornis|
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|
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|
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|
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.
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|
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|
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 skull|
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|
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.
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|
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|
|Artist: Sydney Mohr Shanweiniao|
|Artist: Daniel Bensen Boluochia|
|Credit: Nix Illustration Longipteryx|
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|
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.
|Artist: Jack Wood Rapaxavis|
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.
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|
|A young hatchling enantionithean encased in amber|
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|
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)|
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|
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|
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|
|Artist: Scott Reid Jianchangornis|
|Artist: Jack Wood Zhongjianornis|
|Artist: ©Daniel Benson Chaoyangia|
|Artist: Jack Wood Schizooura|
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 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|
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.
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|
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.
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|
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.
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|
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 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|
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 fossil with predigested fish|
|Artist: Luis Chiappe Hollanda|
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|
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|
|Artist: Jaime Chirinos Ichthyornis stealing fish|
|Artists: Mike Hanso, BA Bhullar Ichthyornis|
|Artist: Masato Hattori Chupkaornis|
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|
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|
|Artist: Gunar Björkman Baptornis|
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|
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|
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|
|Artist: Jaime Chirinos Hesperornis|
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|
|Artists: Julio Lacerda & Henry Sharpe Hesperornis as thief & prey|
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.
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 vertebrae A)Ventral B) Dorsal|
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|
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.
|Neornithean Cladogram Top: Paleognaths Bttm: Neognaths|
|Artist: Franco Tempesta Chicxulub Imoact|
|The Cenozoic Era|
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.
|Gondwana breakup Griem 2007|
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.
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|
|Artist: Piotr Gryz Pseudocrypturus|
|Artist: Scott Reid Paraacathartes|
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|
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|
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|
|Artist: John Megahan Haast’s eagle attacking a pair of moas|
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)|
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|
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|
|Elephant bird egg compared to a chicken egg|
|Elephant bird egg compared to an adult kiwi|
|Cast of elephant bird wingbone|
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|
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|
|Artist: Nicole Fuller Sayo Vegavis syrinx|
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|
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|
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|
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|
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: dinoanimals.com Phorusrhacos|
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.
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|
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|
Genus: Lavocatavis – Middle Eocene Glib Zegdou Formation of Algeria
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|
|Artist: Jose Vega a pelagornithid|
|P. miocaenus skeletal|
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.
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|
|Credit: Slack et al Waimanu tuatahi|
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|
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.
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|
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|
|The 61 mya penguin foot versus extant emperor penguin|
|A hoatzin pair|
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|
|A horned screamer’s claws|
|A duck with forelimb claws|
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|
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|
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|
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:
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)|
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.
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.