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Askeptosaurus italicus

By Ripley Cook

Etymology: Unconsidered Reptile

First Described By: Nopcsa, 1925

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, Disapsida, Neodiapsida, Thalattosauria, Askeptosauroidea, Askeptosauridae

Time and Place: Between 247 and 235 million years ago, from the Anisian to the Ladinian of the Middle Triassic

Askeptosaurus is known from the Besano Formation of Switzerland, as well as the Gejiu Formation of China

Physical Description: Askeptosaurus was a Thalattosaur, a group of strange ancient offshoots, not even proper reptiles - stem-reptiles, not more closely related to any living reptile group than any other - and a fascinating experiment in marine life for land vertebrates completely unique to the Triassic. Like other Thalattosaurs, Askeptosaurus had a long and slender body for streamlined movement through the water. Its tail was built into a paddle, to help with propulsion forward. While their feet were shaped into decent sized paddles, they weren’t adapted into flippers like more thoroughly marine species of reptile. Askeptosaurus also had a long tail and long neck, and an extremely long snout. In fact, this long snout is characteristic of the group of Thalattosaurs Askeptosaurus was a part of. This long, narrow, and pointed skull pushed the nostrils back so they were actually close to the eyes, which themselves were extremely large with a large bony ring around the eye socket. It had very small teeth, though of note - one of its close relatives was toothless, and other Thalattosaurs had distinctively downturned snouts instead. Askeptosaurus had dozens and dozens of teeth all across its mouth, and it also had a lowly-spined back, different from its relatives. It had very slender limbs as well, compared to its relatives. It was probably somewhere between two and three meters long from tail to snout, though that is an extremely rough estimate on my end and no official measurement of its body length has been made.

Diet: Given its many pointed teeth, Askeptosaurus was decidedly a fish eater.

Behavior: Askeptosaurus would have used its paddle-esque feet and hands to steer itself through the water, using the angle and extension of its limbs to turn this way and that. The undulating, long body would have swimped from side to side in order to propel it forward and increase or decrease speed. That extremely long snout was extremely useful for reaching out and grabbing food hiding in rock crevices and other hiding places, as well as for grabbing wriggly and slippery fish and preventing their escape. Askeptosaurus also shows extensive adaptations for deep diving - large eyes suited for low light conditions, as well as a protective ring and strong bones to help in preventing bodily collapse at deep depths. That said, it is at least somewhat a mystery still - did it give birth to live young? Did it live in groups? Given its fairly pad-like limbs, did it spend any time on land? More research on this beautiful group of Triassic creatures is needed to understand their place in the ocean ecosystems.

Ecosystem: Askeptosaurus tended to live near the coasts, still in deep and marine and open habitats but close enough that if it did crawl onto the shore, it would have been able to without going too far out of its way. It seems, based on its distribution, that Askeptosaurus lived throughout the burgeoning Tethys sea, though of course more fossils of this animal in other locations would be helpful to confirm that. It didn’t live near reefs, and preferred open ocean habitats. There was a wide variety of ammonites, brachiopods, snails, and fish - the last of which were, of course, the main prey of Askeptosaurus. As far as reptilian neighbors, there were other Thalattosaurs like Hescheleria and Clarazia; Tanystropheids like Tribelesodon, Tanystropheus, and Macrocnemus; Helveticosaurids like Helveticosaurus and Eusaurosphargis; Placodonts like Paraplacodus and Cyamodus; Ichthyosaurs such as Cymbospondylus and Mixosaurus; Pachypleurosaurus like Keichosaurus, Serpianosaurus and Pachypleurosaurus; Suchians such as Ticinosuchus; and Nothosaurs like Nothosaurus and Lariosaurus. So, an extremely diverse ecosystem - where different marine reptiles had to carve out their own roles for survival - was the cacophony that Askeptosaurus called home.

Other: Thalattosaurs seem to be completely separate from all other reptiles, not even in the crown group - in the Neodiapsids, a group that diverged in the Permian and eventually lead to proper reptiles and their relatives, but Askeptosaurus and other Thalattosaurs broke off from in that time. That means that there should be fossil Thalattosaurs in the Permian, or at least their precursors. Sadly, we do not have them. More research is needed to understand their origins, though their diversity and evolution in the Triassic is fairly clear. Sadly, the end-Triassic extinction killed this beautiful group, and their role in the ecosystem would be replaced by other ,more familiar marine reptiles.

~ By Meig Dickson

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