archosaur – Page 11 – Nix Illustration

Longipteryx

Longipteryx chaoyangensis, an enantiornithine from the Early Cretaceous of China, about 120 million years ago. With a body length of only around 15cm (6″), it had a long snout tipped with a few hooked teeth and feet capable of perching – features that indicate it may have lived very similarly to modern kingfishers, feeding on fish and small invertebrates in its swampy forest habitat.

The enantiornithines were a sort of “cousin” lineage to modern birds. Most had toothy jaws and clawed wings, and the wide variety in their skull shapes suggests that they were specialized for many different dietary niches. The entire group went extinct during the K-Pg mass extinction and left no living descendants, but during the Cretaceous they were the most widespread and diverse group of birds*, with fossils currently known from every continent except Antarctica.

* Depending on how you define “bird”.

Pisanosaurus

Pisanosaurus mertii from the Late Triassic of Argentina (~228-216 mya).

Known only from a partial skull and a few pieces of its skeleton, this 1m long animal (3′3″) is usually considered to the be the earliest known member of the ornithischian dinosaurs – but some recent studies have thrown that into question, suggesting that it might not even be a dinosaur at all.

Instead it may have been a member of the silesaurids, Triassic dinosauriforms that were close cousins to the dinosaurs but not quite true members of the group. Small and lightly-built, silesaurids had long front limbs and may have been at least partially quadrupedal, and some showed evidence of herbivory with beaks at the tips of their snouts.

Of course, if the “oldest ornithischian” is actually a silesaurid, we’re left with no fossil record at all for ornithischians until the start of the Jurassic. And that brings back up the controversial question of where they actually originated…

Halszkaraptor

Halszkaraptor escuilliei, a dromaeosaurid (“raptor”) dinosaur from the Late Cretaceous of Mongolia (~75-71 mya). It’s known from a single near-complete skeleton and would have been about the size of a modern mallard duck, around 60cm long (2′).

It had some very odd features for a raptor, with many small sharp backwards-pointing teeth, crocodile-like sensory pits on its snout, a long flexible neck, small flipper-like arms, a relatively short tail, and a more upright body posture than its other relatives. All these traits together suggest it may have been semi-aquatic, which is a pretty big deal since the only other group of non-avian dinosaurs known to have developed adaptations for life in the water were the spinosaurids.

The fossil was originally illegally excavated by fossil poachers and was owned by private collectors for several years, but it has now been returned to science and is due to be repatriated to Mongolia. With its odd anatomy and the exact origin of the specimen being unknown, there’s some skepticism about whether Halszkaraptor represents a genuine animal or an elaborate fake chimera – but synchrotron scans of the fossil and its similarity to previously-discovered more fragmentary short-armed raptors like Mahakala suggest that it is real, and it really is that weird.

Ikrandraco

Ikrandraco avatar, a pterosaur from the Early Cretaceous of China (~120 mya). Although it was close relative of the well-known Pteranodon it was much smaller, with an estimated wingspan of around 1.5m (4′11) – similar in size to a large seagull.

Its name was based on the fictional ikran creatures from the 2009 movie Avatar, in reference to similarity of the the large crests on their lower jaws.

*Ikrandraco*’s skull (scale bar = 5cm)
[*image source*]

A hook-shaped projection at the back of the crest may have been an attachment point for a pelican-like throat pouch. The paleontologists who described Ikrandraco also suggested that its crest could have been used for skim-feeding, although this is a highly controversial idea among pterosaur specialists.

Zuul

Zuul crurivastator, an ankylosaur from the Late Cretaceous of Montana, USA (~75 mya).

One of the most complete ankylosaurids ever found in North America, it’s known from a full skeleton about 6m long (20′). Much of its bony osteoderm armor is preserved in life position, along with skin impressions and the remains of keratinous scales and spike sheaths – although so far only the skull and tail have actually been fully prepared and described.

(The fuzz on this reconstruction is highly speculative, but since it’ll likely end up inaccurate anyway once of the rest of the body is fully described… why not have some fun with it?)

Its genus name was inspired by its skull’s resemblance to Zuul the Gatekeeper from the 1984 movie Ghostbusters, while its species name translates to “destroyer of shins” in reference to its especially large tail club.

Mirischia

Mirischia asymmetrica, a theropod dinosaur from the Early Cretaceous of Brazil (~112-99 mya). Although known only from its hips and a few other partial bones, these pieces were so well-preserved that it was given a genus name that translates to “wonderful pelvis”.

In life it would have been about 2m long (6′6″), but since the known fossil represents a subadult its full-grown size may have been a little bit larger. It was probably a member of the compsognathids, closely related to Compsognathus and Aristosuchus – which would make it the only representative of that family currently known from the Americas.

The ischium bones of Mirischia’s pelvis were oddly asymmetrical, hence the species name ‘asymmetrica’, with one side featuring a hole and the other side only having a notch in the same position. The fossil specimen also had thin-walled bird-like bones, and soft-tissue impressions of intestines and a posterior air sac.

Pakasuchus

Pakasuchus kapilimai, a notosuchian crocodyliform from the mid-Cretaceous of Tanzania (~105 mya). This 50cm long animal (1′8″) had an elongated body and relatively long limbs, and would have been an active terrestrial predator chasing after fast-moving small prey like insects.

The bony osteoderms on its body were much smaller and sparser than those found on most of its relatives – except for its tail, which was still heavily armored.

It also had some of the most complex teeth of all known crocodilians, with surprisingly mammal-like ‘canines’ and ‘molars’ that gave it the ability to chew its food.

Turtle-jawed moa-nalo

The turtle-jawed moa-nalo (Chelychelynechen quassus) was a large flightless goose-like duck from the Hawaiian island of Kaua‘i. About 90cm tall (3′) and weighing around 7kg (15lbs), these birds and their relatives were descended from dabbling ducks and existed on most of the larger Hawaiian islands for the last 3 million years or so – before going extinct around 1000 years ago following the arrival of Polynesian settlers.

Chelychelynechen had an unusually-shaped bill, tall and broad with vertically-oriented nostrils, convergently similar to the beak of a turtle. It would have occupied the same sort of ecological niche as giant tortoises on other islands, filling the role of large herbivore in the absence of mammals.

Herrerasaurus

One of the earliest known dinosaurs, Herrerasaurus lived during the Late Triassic (~231 mya) in what is now Argentina, South America. It was a fairly lightly-built bipedal carnivore, with the largest specimens reaching sizes of just over 5m long (16′4″).

The exact classification of herrerasaurids is still somewhat unclear, with different analyses putting them in different positions on the early dinosaurian family tree. They’re generally considered to at least be closely related to basal theropods – but a recent analysis that reshuffles dinosaur relationships suggests their resemblance to the theropods might be a result of convergent evolution, with them being the sister group to sauropods instead.

Teleocrater

Teleocrater rhadinus from the Middle Triassic (~245 mya) of Tanzania. Measuring about 2.5m long (8′2″), it was one of the earliest known members of the avemetatarsalians – the dinosaur-and-pterosaur (or “bird-line”) branch of the archosaurs. Its fossils have been known for over 80 years, but it was only very recently given an official name and classification following the discovery of additional specimens in 2015.

It turned out to be rather different from what paleontologists had expected an early bird-line archosaur to look like. Instead of being a bipedal basal-dinosaur-like animal, Teleocrater was actually a quadruped with more crocodilian-like limbs and oddly elongated neck vertebrae.

I’ve done two variations of the image today – both with and without a little speculative proto-fuzz.