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Vancleavea campi an archosauriform that lived during the late Triassic in North America. It had an estimated length between 1.5 and 3.5 meters and imbricated and mostly carinated osteoderms covered its entire body.
Artwork by Gabriel Ugueto
Days 1-4 of my Croctober2025 list :^]
marginalia ft Howl
I am seeing lots of great discussion here on the usefulness of AI software to assist with paleontological matters, I would like to link a source that many of you may find helpful on this topic. Paleontologist Mike Taylor made a post on his blog Sauropod Vertebra Picture of the Week discussing the usage, and failure, of ChatGPT to do any real paleontological work.
Link: https://svpow.com/2025/02/14/if-you-believe-in-artificial-intelligence-take-five-minutes-to-ask-it-about-stuff-you-know-well/
As a further test, I also replicated his results with ChatGPT myself. The image is attached. ChatGPT combined a real journal alongside a completely fake paper. Vancleavea campi was established in Long & Murry (1995) and not in 2006. The paper listed is whole heartedly not real, and the given specimen number if the holotype specimen is also completely fabricated. For those who are interested, the correct holotype specimen number is PEFO 2427 and resides not at the University of Michigan but instead at Petrified Forest National Park.
Generative AI, yes even CoPilot and others, cannot do real work. This is because they don’t know what they don’t know. They aren’t intelligent and lack the ability to do anything really at all.
The citation looks real! It feels real! But, of course, this is a farce. That’s the issue. To the uninformed, a lay person, this appears completely and totally true. I urge anyone using AI for academic purposes to stop using it immediately. It’s the academic equivalent of half-assing your chores as a child. Yes, shoving your toys in the closet does make the bedroom look cleaner but a closer examination will always have you needing to do 2x the work than if you just did it correctly in the first place.
Vancleavea campi is wonderfully weird, so it, of course, deserves a quick drawing :)
Vancleavea campi.
Archovember Day 21: Vancleavea campi
Vancleavea campi, an armored archosauriform from the Late Triassic of western North America, had a unique morphology that wildly differs from any other known basal archosauriform. It was a semi-aquatic or fully aquatic creature with a fanged, fish-like skull, short limbs, a long body, and five to six different types of osteoderms covering its body (which I’m not sure I depicted correctly; they’re very confusing.)
Most unique are the osteoderms on the tail. There is an enlogated plate on each vertebrae that together make up a paddle tail. This is very different from the tall neural spines seen on spinosaurus or other semi-aquatic archosauriforms.
The largest complete specimen found was around 3.9 feet long, though isolated pieces from other specimens suggest it could have grown larger. Vancleavea likely fed on fish, amphibians, and other aquatic prey. It is also speculated to have been an ambush predator, similar to modern day crocodilians.
Vancleavea campi
By Tas Dixon
Etymology: Named after Phillip Van Cleave
First Described By: Long & Murry, 1995
Classification: Biota, Archaea, Proteoarchaeota, Asgardarchaeota, Eukaryota, Neokaryota, Scotokaryota, Opimoda, Podiata, Amorphea, Obazoa, Opisthokonta, Holozoa, Filozoa, Choanozoa, Animalia, Eumetazoa, Parahoxozoa, Bilateria, Nephrozoa, Deuterostomia, Chordata, Olfactores, Vertebrata, Craniata, Gnathostomata, Eugnathostomata, Osteichthyes, Sarcopterygii, Rhipidistia, Tetrapodomorpha, Eotetrapodiformes, Elpistostegalia, Stegocephalia, Tetrapoda, Reptiliomorpha, Amniota, Sauropsida, Eureptilia, Romeriida, Diapsida, Neodiapsida, Sauria, Archosauromorpha, Crocopoda, Archosauriformes, Eucrocopoda, Proterochampsia?, Doswelliidae?
Status: Extinct
Time and Place: 228 to 203.6 million years ago, in the Norian of the Late Triassic
Vancleavea is best known from the Petrified Forest in Arizona and Ghost Ranch in New Mexico, but is found throughout the Chinle Formation in Arizona, New Mexico, Texas and Utah in the southern United States. It is also known from the Tecovas Formation in Texas, and the Redonda and Bull Canyon Formations in New Mexico.
Physical Description: Vancleavea is a peculiar reptile, even by Triassic archosauromorph standards. It effectively resembles an armoured, scaly eel with tiny legs, a long neck, the tail of a crocodile and a frighteningly fang-toothed skull. The largest complete specimen is approximately 1.2 metres (3.9 feet) long, although isolated pieces from other specimens indicate it could grow larger. Most of its body is covered in an array of overlapping bony osteoderms that come in 5 different shapes on the main body, throat, underbelly, limbs and tail (as well as possibly some strange spike-like osteoderms of unknown position). Uniquely, the osteoderms on the tail are tall and flat from side to side, forming a tall fin along the top of the tail for swimming. No other tetrapod—except for the closely related Litorosuchus—has a tail fin like this (usually they are made of tall neural spines from the tail bones).
Vancleavea’s skull is also unusual, as it is very robust and solid, despite the relatively thin and pointed snout. The back of the skull is boxy and has completely closed over the upper temporal fenestra, leaving just the very large lower temporal fenestra. The antorbital fenestra in front of the eyes, a typical feature of archosauriform reptiles, has also been lost, and the snout is short with nostrils that point directly upwards. The jaw bones of Vancleavea are heavily pitted and have a rough texture, which combined with the large teeth imply Vancleavea lacked lips and had exposed fangs, similar to crocodiles. Vancleavea had three fangs on each side of its jaws, one at the front, one on the lower jaw, and another on the upper jaw behind the bottom fang. The dentary fang slotted into a gap in the upper jaw when the mouth was closed, again similar to crocodiles.
The body of Vancleavea is long and tubular, enhanced by both the unusually long neck and the small size of its limbs. It’s unlikely Vancleavea’s limbs were strong enough to lift its body off the ground on land, and in fact the forelimb is so reduced that the shape of some its finger bones suggests it had even lost the claws on its hands. All in all Vancleavea is very clearly built to be semi-, if not almost entirely, aquatic, swimming with a sinuous, eel-like motion and rarely crawling onto land, perhaps only to lay its eggs.
Diet: The massive, serrated fangs and conical teeth indicate Vancleavea was carnivorous, likely feeding on fish and other aquatic prey, such as small temnospondyl amphibians.
Behavior: Vancleavea is almost certainly semi-aquatic, using its deep, finned tail to scull through the water similar to living crocodilians. It’s speculated that Vancleavea lived as an ambush predator, lunging forward to snag prey in its fangs. It lived in slow-moving freshwater environments, and its elongated, sinuous body would have been perfect for winding through plants and logs and other obstacles in the water.
Ecosystem: Vancleavea is known from much of the Chinle Formation, one of the most well known Late Triassic formations in the world, and its longevity means that it coexisted with a wide variety of other animals. There were of course the dinosaurs, including the likes of Coelophysis, Chindesaurus and Daemonosaurus, along with other dinosauriforms such as silesaurids and the lagerpetid Dromomeron, as well as early pterosaurs. Pseudosuchian archosaurs were incredibly abundant, such as the numerous herbivorous aetosaurs and Revueltosaurus, the dinosaur-like poposauroids including the herbivorous beaked Shuvosaurus and Effigia, as well as the predatory Poposaurus. Rauisuchid pseudosuchians were among the top predators, such as Postosuchus, while small long-legged crocodylomorphs like Hesperosuchus and Parrishia chased after smaller prey. Various other archosauromorphs were present too, including the bizarre drepanosaurs, herbivorous allokotosaurs such as Trilophosaurus and an unnamed azendohsaurid, and the strange armoured Doswellia, possibly Vancleavea’s closest relative. There was even an early turtle, Chinlechelys, one of the earliest known to have a fully formed shell, and a relative of the tuatara, Whitakersaurus. The only definitively known synapsid from the Chinle is the large herbivorous dicynodont Placerias.
In the water, Vancleavea would have coexisted with numerous species of giant phytosaurs—crocodile-like reptiles that may-or-may-not be pseudosuchians—such as Leptosuchus and Machaeoprosopus, as well as the predatory temnospondyl amphibian Anaschisma (formerly known as Koskinonodon). Vancleavea’s heavy armour may have been necessary protection against these predators, which could have had jaws almost as long as it was! Fish were abundant in the freshwater ecosystem, with various ray-finned fish such as the pike-like Saurichthys, the large lungfish Arganodus, freshwater sharks such as Xenacanthus, and even a freshwater coelacanth, Chinlea. Many of these fish grew to as large or larger than Vancleavea, and may have competed with it or even preyed upon it (at least as juveniles).
Vancleavea also coexisted with several other, more mysterious reptiles that are mostly only known from teeth. One of these, Acallosuchus, was discovered close by to the original specimen of Vancleavea. The skull and skeleton were originally suggested to belong to the same animal, but we now know Vancleavea had a very different skull to Acallosuchus. Supposedly its skull was long, pointed and triangular, with a knobbly texture on the bones. I say “supposedly” because the skull disintegrated while it was excavated, and all that’s left is a crude drawing and a few pieces of bone. The identity of Acallosuchus remains a mystery. Other mysterious species that Vancleavea coexisted with are the former ornithischians Tecovasaurus and Crosbysaurus, Colognathus, Palacrodon, the possibly venomous Uatchitodon, and the extremely enigmatic Kraterokheirodon known only from two teeth so unlike any known tetrapod alive or extinct it can only be classified as Amniota incertae sedis! Vancleavea was once in the same boat as all these creatures, known only by pieces of the skeleton and its armour, and with any luck, Acallosuchus and the other mystery creatures will end up like Vancleavea and turn up some complete skeletons one day.
Other: Vancleavea is known from throughout the Chinle Formation and several other localities in the southern US, however, most of these specimens consist of isolated bones and osteoderms. The Chinle Formation covers many tens of millions of years from top to bottom, and it’s unlikely the single species V. campi was that long-lived (its range spans a whole 20 million years!). Variations between some specimens suggest that there may be more diversity within Vancleavea then we currently recognise. However, until better specimens are found and can be compared, we can’t be sure how Vancleavea evolved and changed throughout the course of the Chinle.
Vancleavea has a fairly complicated history, the holotype was first discovered in the Petrified Forest by fossil collector Phillip Van Cleave, who lent it his name, but it wasn’t described and named until 1995 and still only consisted of a fragmentary skeleton. Nearly complete specimens from Ghost Ranch were discovered in 1982, but they wouldn’t be recognised as Vancleavea until decades later. In 2008, new specimens from the Petrified Forest were published, but Vancleavea still had to wait another year before the Ghost Ranch specimens were extensively described and its strangeness could be fully appreciated.
Until recently, Vancleavea was the only known stem-archosaur of its kind known in the world, and its relationship to other archosauriforms was enigmatic. However, the discovery of the closely related Litorosuchus from China indicates that the Vancleavea-family (“vancleaveans”) was indeed more diverse and widespread. Unlike Vancleavea, Litorosuchus was marine, and had a much longer, almost spinosaur-like snout. The position of Vancleavea in the archosauromorph tree is still uncertain, but it has been suggested to be a type of proterochampsian, a group of typically crocodile-like reptiles closely related to archosaurs proper. Particularly, it has been allied to the family Doswelliidae, a peculiar family of proterochampsians with similarly strange armour and skeletons. Regardless of where it truly belongs, Vancleavea is at least generally agreed to be a fairly derived archosauriform, quite close to the crown group of Archosauria, albeit having evolved down a very unusual, unique route all of its own.
~ By Scott Reid
Sources under the cut
