#protorosaur

[saritapaleo]

Archovember 2025 Day 2

Protorosaur Dinocephalosaurus orientalis, of Middle Triassic, China!

Second on our Archovember list this year is the bizarre Middle Triassic protorosaur, Dinocephalosaurus orientalis. Like their relatives, the tanystropheids, Dinocephalosaurus had a long neck with fang-like teeth used for catching fish. But, unlike the tanystropheids, its neck was not lengthened through the elongation of cervical vertebrae, but rather the addition of at least 27 individual neck vertebrae, giving it much higher flexibility. Also unlike the tanystropheids, it had paddle-like flippers which would have given it a purely aquatic lifestyle. Dinocephalosaurus’ long neck would have allowed it to sneak up on potential prey without its larger body being detected. One Dinocephalosaurus specimen was preserved with an embryo that suggests it gave live birth, making it the first known viviparous archosauromorph, (aside from possibly metriorhynchids).

Dinocephalosaurus orientalis was first described from the Upper Member of the Guanling Formation, with additional specimens discovered in the Luoping locality. Inhabiting the Middle Triassic seas of China, it would have lived alongside icthyosaurs such as Mixosaurus and Xinminosaurus, a wide variety of early sauropterygians like Keichousaurus, Wumengosaurus, Dianopachysaurus, Nothosaurus, and Placodus, and other marine reptiles like Sinosaurosphargis.

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[ye-oldroderich]

wow ignore that i havent posted here since last year. ANYWAYS !!!! somehow i forgot to post these guys alongside my Megaraptor i drew in november so 😭 here's some more fandinos for Paleo Pines !!!

"fandinos" being sorta misleading though since neither of these guys are dinosaurs lol. regardless, up first we have Tanystropheus who is infinitely ridiculous. then we have Sharovipteryx, who is equally infinitely ridiculous. both of these guys lived in the Triassic - and surprisingly, are likely related!

[alphynix]

Dinocephalosaurus orientalis was a fully aquatic protorosaur reptile living in what is now southwest China during the mid-Triassic, about 244 million years ago.

Up to 6m long (~19'8"), it had a long serpentine body with paddle-like limbs and an especially elongated neck – but despite the superficial similarities to its semi-aquatic cousin Tanystropheus, Dinocephalosaurus' long neck appears to have been independently evolved.

Much like the similarly-shaped elasmosaurs, its neck may have had a "stealth" function, allowing it to bring its jaws closer to targets before the rest of its body was visible, then using side-to-side snapping bites to catch its prey in its interlocking "fish-trap" teeth.

A preserved well-developed embryo inside one specimen also suggests that Dinocephalosaurus gave birth to live young, making it one of only two archosauromorph lineages known to have ever evolved this reproductive strategy.

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[alphynix]

Tanystropheus is one of the classic Triassic weirdos, a bizarre archosauromorph easily recognizable with its ridiculously long neck.

Mainly known from mid-Triassic deposits on the Swiss-Italian border, dating around 247–235 million years ago, fossils of the species Tanystropheus longobardicus have been found in two different "morphs" – small forms less than 2m long (6'6"), and larger ones up to 6m long (19'8").

For a long time the smaller fossils were thought to be juveniles, but while they certainly had juvenile-looking facial proportions they also had very different teeth compared to the larger forms. They had pointed teeth at the front of their mouths and multi-cusped cheek teeth further back, and the "adults" had jaws containing only the pointed teeth, suggesting very different diets and lifestyles between the two size classes.

Extreme changes in dentition and diet during maturation aren't unheard of in fossil species, but something particularly odd was going on here. Larger forms over 2m long always had just the pointed teeth, and there were no signs of intermediate tooth arrangements at all.

And a new study using x-ray microtomography has given an answer: they weren't actually the same species!

Turns out the smaller Tanystropheus longobardicus were all skeletally mature adults, already fully grown at that size. The larger ones were a completely separate species occupying a different ecological niche to their smaller relatives, and have been named Tanystropheus hydroides in reference to the mythical hydra.

Comparison of the skulls of T. hydroides and T. longobardicus

[ From fig 3 in Spiekman, S. N. et al (2020). Aquatic Habits and Niche Partitioning in the Extraordinarily Long-Necked Triassic Reptile Tanystropheus. Current Biology. https://doi.org/10.1016/j.cub.2020.07.025 ]

While the exact lifestyle of Tanystropheus is an ongoing paleontological argument, Tanystropheus hydroides at least appears to have been much more on the aquatic side of things, with nostrils positioned on the top of its snout and its pointed teeth forming a "fish trap" in its jaws.

Stomach contents suggest it mainly ate fast-moving aquatic prey like fish and cephalopods, but its body wasn't really adapted for strong swimming and so it couldn't have been catching them via active pursuit. Instead it was probably an ambush predator hunting in a similar manner to some plesiosaurs, using its incredibly long neck and relatively small head to carefully approach prey species without the rest of its body startling them, and then catching them with fast snapping sideways lunges.

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[alphynix]

One of my favorite palaeontological discoveries of 2016 also involved one of my favorite extinct animals: the odd little “monkey lizard” Drepanosaurus.

Living during the Late Triassic of Europe and North America (~218-212 mya), this reptile measured about 50cm long (20"). It was already known to have some particularly weird anatomy, featuring a humped back, grasping feet, a prehensile tail ending in vertebrae modified into a pseudo-claw, enormous claws on the second finger on each hand, and a bizarre arrangement of its forearm bones.

In 2016, new fossils gave us a better look at those arm bones, and they turned out to be even stranger than previously thought. As well as the radius and ulna being unusual, several wrist bones were also heavily modified and elongated, creating an arm setup unique among all known tetrapods. This may have been a specialization for “hook-and-pull” digging, ripping up tree bark to get at burrowing insects -- but now the real mystery is why no other tetrapods have ever managed to modify their limb bones to this sort of extreme.

[alphynix]

Mecistotrachelos aperos, a gliding reptile from the Late Triassic (~225 mya) of the eastern United States. Known from only two specimens, it was probably around 25cm in length (10″), and was the first fossil taxon to be described based entirely on CT scans. Although its exact evolutionary relationships are still unclear, it’s currently thought to be a protorosaur related to Triassic oddballs like Tanystropheus, Sharovipteryx, and the drepanosaurs.

It had elongated ribs that supported a gliding membrane, a feature that convergently evolved several times in different fossil reptile groups and can be seen today in the flying dragon lizards. Unlike other known rib-gliders, however, Mecistotrachelos had a particularly elongated neck -- which even inspired its name, “soaring longest neck”.

The ribs along the leading edge of its gliding membrane were also unusually thickened, with enlarged joint articulations, suggesting that it might have had specialized muscle attachments to precisely control the position and curvature of its “wings” while in flight.

[ornithopsis]

hey, i saw that you said you're p knowledgeable about protorosaurs. I'm not the same anon, but i've also got Questions about protorosaurs. why are they so singularly weird? like, i mean, everything else is weird, too, but- tanystropheus? drepanosaurs? sharovipteryx? are not just weird, they're Super Fucking Weird. so why are protorosaurs so weird and especially diverse, comparatively? it's not just a garbage can order where they toss all the weird things they don't know how to classify, right?

I think that a major part of it is just the general weirdness of Permo-Triassic reptiles. However, I have to admit that protorosaurs seem to cluster together a higher-than-normal amount of weirdness in a relatively small clade. They actually aren’t alone in this regard–last year, a clade called Allokotosauria was discovered that groups together trilophosaurs (iguana-like reptiles that had beaks and molars, some of which looked truly bizarre) with the prosauropod mimics Azendohsaurus and Pamelaria.

Protorosaurs are not a wastebasket taxon, as some cladistic analyses have supported grouping drepanosaurs, tanystropheids, and some other things together. However, their monophyly is still questionable–around a decade ago, Prolacerta was recognized as being more closely related to archosaurs, and things have gone back and forth about whether drepanosaurs belong in the group or not. A narrow grouping of some protorosaurs–e.g. Macrocnemus, Langobardisaurus, and Tanystropheus, does appear to be monophyletic, but it is unclear whether Protorosaurus is also within that clade. I’ll still call this group “protorosaurs” for now, but since Protorosaurus might not be in the clade it could be a misnomer. Overall, protorosaurs in the broad sense seem to be a paraphyletic grouping of basal archosauromorphs that don’t belong to other clades such as Archosauriformes or Rhynchosauria. 

As for Sharovipteryx, I don’t think any competent researcher has ever included it in a cladistic analysis, so it’s hard to say what it is right now. Other weird Triassic reptiles, such as Mecistotrachelos, Dinocephalosaurus, and Fuyuansaurus, might also be “protorosaurs” in the narrow sense, but also need cladistic testing. If these are confirmed to be protorosaurs, the clade would still be a pretty diverse and weird group!

Essentially, some of the weirder protorosaurs might not actually belong to that clade and overall their weirdness isn’t too exceptional for the Triassic. Still, the weirdness and diversity of protorosaurs is very interesting. It seems likely that they were lucky enough to be adaptable generalists living in the immediate aftermath of a devastating mass extinction. They, along with other such reptiles, had a dizzying array of newly-opened niches to compete for, allowing for a huge radiation in diversity.

[astronomy-to-zoology]

Genus: Tanystropheus

...a genus of Protorosaurs that lived during the Middle Triassic period, with fossils found in Europe, the Middle East and China. Tanystropheus's most striking feature was its extremely long neck which measured around 3 m (10 ft). Due to this Tanystropheus is often reconstructed an aquatic reptile, which is justified due to the fact that has been found at semiaquatic fossil sites. Due to the presences of a long snout with sharp interlocking teeth, Tanystropheus was thought to be a piscivore as well.

Classification

Animalia-Chordata-Reptilia-Protorosauria-Tanystropheidae-Tanystropheus

Image: Tommy and Ghedoghedo