Two artists’ renderings of “Proavis”, a hypothetical bird ancestor. The lizard-limbed would-be creature is certainly a product of its time, as birds were once thought to be descendants of the clade Pseudosuchia (the name Crurotarsi is more commonly used today and generally includes the same taxa). Traditionally, Pseudosuchia was considered a suborder of the now-obsolete order Thecodontia.
Gerhard Heilmann laid out the hypothesis of a pseudosuchian ancestry of birds in his highly influential 1926 book The Origin of Birds, which was considered the last word on the subject of bird evolution for several decades after its publication. Heilmann acknowledged a close relationship between non-avian theropod dinosaurs and birds but rejected the notion that the former directly gave rise to the latter. One example of his reasoning was that birds have a furcula (wishbone), a feature which non-avian theropods did not appear to him to possess (though we now know otherwise), yet ancient reptilian fossils that predated dinosaurs did show clear evidence of a furcula-like structure. Though the evidence to which we now have access overwhelmingly supports the hypothesis that birds are indeed the descendants of dinosaurs rather than the crocodile-like “thecodonts”, much of the book’s research remains of interest.
A study of Saurian morphology: Pterosauria (part 3)
In which our old friend Dsungaripterus returns with two friends for Pterosaur Ptuesday! Sadly, I’m done with pterosaurs and will have to move on to Pseudosuchia—which I have very minimum knowledge of. If someone here can help me with dem crocs I’d be grateful.
I will also take a day or two of break from this project since I need to catch up on another (plus my wrist kinda hurts). So expect the first batch of Pseudosuchians in 4-5 days.
P.S.: Mark Witton retweeted my first set and I’m still asdjlaksds-ing about it.
A couple sketches based on ideas I’ve had for a speculative evolution project I’m involved with. The top one is a dicynodont, while the one below is a cursorial shuvosaurid, descended from something similar to Shuvosaurus or Effigia.
Although Prestosuchus chiniquensis was a large animal with big claws and a huge head with sharp-toothed jaws, it was not a dinosaur. This creature belongs to a larger group called Pseudosuchians, which also includes modern day crocodilians.
Today, these creatures are only represented by a couple dozen species, but back in the Triassic, they were extremely diverse, and in direct competition with early dinosaurs. Late in the Triassic, multiple extinction events led to the demise of many major Pseudosuchian lineages, opening up niches for dinosaurs to take advantage of. Thus, the rest of the Mesozoic became the age of dinosaurs. Learn more about this extinction in the most recent episode of Shelf Life.
This specimen is a reconstructed composite of several Prestosuchus specimens collected in Brazil and dating from the Late Triassic, about 210 million years ago.
We’re typically taught that dinosaurs lived for three geologic periods–the Triassic, Jurassic, and Cretaceous. This is true, but Triassic dinosaurs were wussy little things. The planet was dominated by their cousins: the pseudosuchians, or false crocodiles. Imagine crocodiles with their legs held directly under them, so that they could gallop like a horse. They were diverse, and they were scary.
So far, we’ve been telling other creatures from dinosaurs by their skulls, but pseudosuchians and dinosaurs (and the major group that includes dinosaurs, the ornithosuchians) are both archosaurs. Pseudosuchians are represented today by crocodiles, and ornithosuchians by birds. Archosaurs are diapsid reptiles, and in addition to the two characteristic diapsid skull-holes, they have a couple extras.
No, the difference between pseudosuchians and dinosaurs is in the ankle. Pseudosuchians have a complex ankle joint that fits together a bit like two puzzle pieces. Dinosaurs have a more simple, hinge-like joint.
Another hint is that pseudosuchians mostly look like terrifying crocodile-y things, often with an upright posture so they can run and chase things really effectively. Also, they’re older than the vast majority of dinosaurs and all of the big charismatic ones. Apart from crocodiles, pseudosuchians barely survived the Triassic. Their extinction is what really allowed dinosaurs to thrive.
Last year, a new species of crocodilian relative was discovered from Late Triassic North Carolina. Dubbed Carnufex carolinensis - “the Carolina butcher” - this animal grew up to nine feet long, and was capable of walking on its hind legs.
Carnufex is interesting for being a basal crocodylomorph - a member of the clade that includes modern crocodilians. This proves that crocodylomorphs were vying for apex-predator positions during the Late Triassic, along with early theropods, as well as several other groups of pseudosuchians known as rauisuchids and poposauroids.
This extreme diversity of predators proved unsustainable, and many of these animals - including Carnufex - died out by the time the Triassic period was over. Theropod dinosaurs became the top predators for hundreds of millions of years afterward, while Carnufex’s surviving relatives were relegated to less dominant positions.
Way overdue, I know. By now most of you must have pledged your money elsewhere, but this is mostly for the few loud followers who demanded the thing. I figured a couple extra bucks a month should help me with groceries. In short, these are the two major things that you can expect to show up on my Patreon.
Daily Drawings Basically all the things you see from me here on a daily basis. Except in high-resolution. That you can use for any personal purpose. Sure, one month from now my daily saurians will be over, but I’ll keep drawing animals on a daily basis, albeit under different themes, because it does help me a lot with anatomy. And the files are all yours to use, because why not.
P.S., in fact, I’m planning another series that I might run together with the daily saurians, which means I may do more than 2 drawings a day when I’m not working on something else.
The Srs Stuffs™ In parallel to the daily drawings, I will also create one (or two) bigger, more elaborate works per month. These may range from artistic interpretation of scientific articles to fancy shmancy infographics done in collaboration with sciencepersons on tumblr (hint: @cyan-biologist is my first victim). In addition to regular WIPs, I will also upload the low-resolution PSD file with annotations to explain each step of my creative process, including the fails and sharp turns I take to achieve the final result. Higher tier patrons may also opt to receive these srs stuffs as a t-shirt.
But it’s mid February already I KNOW, I’m lame. As an apology, I’d like to kick this off by offering a mega pack for you early burbs. All patrons pledging this month will receive all Saurian Morphology drawings I’ve done up to the end of February (approx 65 drawings). Higher tier patrons will receive the PSD files of all three #pokemon20 tribute drawings.
I hope that’s good enough to convince you lot, eh.
Desmatosuchus, one of that mighty lineage of armor-backed pseudosuchians, the aetosaurs (or as Darren Naish once aptly termed them, the armadillodiles). It joins its distant relatives Shuvosaurus, Effigia, and Simosuchus in defying the carnivory we may come to expect from croc-line archosaurs. The shovel-like snout and peg-shaped teeth of aetosaurs would seem to pin them as herbivores.
All the same, it has been postulated before that these were instead adaptations for insectivory, and an abstract has been around since 1995 toting around the supposed discovery of a carnivorous aetosaur. Personally I wouldn’t be surprised if they were something more akin to boar-like, omnivorous scavengers of Triassic forests.
Desmatosuchus was among the larger members of the family, spanning about 5 meters (16 feet) in length. It’s known from the Late Triassic of Texas.