rhynchosaur

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Genus: Hyperodapedon

…an extinct genus of rhynchosaurs (a group of archosaur-like reptiles) that lived during the late Triassic period. Hyperodapedon was a heavily built animal and like other rhynchosaurs it had a ‘beak’ with a set of rodent-like teeth, it also had several rows of teeth on its upper jaws and a single row on its lower jaw. These teeth allowed it to create a powerful chopping action. It used these chopping teeth to feed on Triassic plants like seed ferns. Their decline has been attributed to the extinction of these plants at the end of the Triassic.

Phylogeny

Animalia-Chordata-Reptilia-Rhynchosauria-Hyperodapedontidae-Hyperodapedontinae-Hyperodapedon

Images: Nobu Tamura and Daderot

Hyperodapedon, a 1.3m long (4'3") rhynchosaur from the Late Triassic, about 231-216 million years ago. It was found throughout most of the supercontinent of Pangaea, and its remains have been identified all over the modern world  – including Argentina, Brazil, India, Scotland, Canada, and the USA.

Rhynchosaurs were herbivorous reptiles related to the archosaurs, and seem to have been very common across Pangaea, making up around half of the specimens found in some locations. They had tubby bodies, semi-erect limbs, large claws on their hind feet, and triangular skulls with powerful jaw muscles.

Later forms like Hyperodapedon also had bizarre jaws, with the frontmost bones of the upper jaw (the premaxillae) curving downards to form a beak-like structure. Although many reconstructions give them an actual “beak” (or make them look like reptilian mole-rats), there doesn’t seem to be evidence of any sort of keratinous covering on these bones – and only the very ends show evidence of wear, suggesting that the tips were exposed but the rest was wrapped in softer tissue. It’s entirely possible that their heads were actually a lot more “normal-looking” than some of the shrink-wrapped nightmares out there.

I’ve given this one little protruding upper “tusks” but otherwise made the head more fleshy. Which certainly helps make it look a lot less like some sort of weird alien.

Also eyespots. Because eyespots are awesome.

Rhynchosaurus.
This was a small rhynchosaur (diapsid reptiles related to the archosaurs), and being 2 feet long one of the smallest known of its group. Footprints believed to belong to Rhynchosaurus- suitably named Rhynchosauroides -have been found in the Alps. It had a semi-erect posture like a crocodile and its hind feet appear to have been adapted for scratching and digging. It had two large teeth at the front of its head, and its skull structure suggests that it had a good sense of smell, but poor hearing.

Imagine a large, reptilian naked mole rat.

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That trilobite preparation post made me nostalgic for the time when we found a rhynchosaur skeleton (well we assume it’s a rhynchosaur since they’re very common in that area) during the field trip of my paleontology class. We found it late in the evening on the last outcrop we visited that day, called Predebon (Santa Maria formation, Triassic) and me, a colleague and a friend of my professor went back there the following morning to dig more of it.

We didn’t dig all of it since we still had outcrops to visit, but we uncovered enough to see some ribs, femur and tibia.

I couldn’t go back there with the team that later returned to fully uncover the fossil, since I had tests, but from what I’ve seen from the block they brought back the skeleton is quite well preserved, although the skull is fragmented. They’re exposing it in the block itself, so they can show people how fossils look like while they’re on the field.