Sunday, February 2, 2014

One crazy Sauropterygian

You won’t believe what crazy prehistoric critter has just been described from the Middle Triassic (Anisian) Luoping fauna of the Yunnan province of China. The site is world famous for his rich collection of well-preserved fossils of shallow sea marine reptiles that include primitive ichthyosaurs, protorosaurs and pachypleurosaurs.

Atopodentatus unicus is a Sauropterygian with a typical body plan of a primitive Sauropterygian, elongated, with a long tail, and paddle-like limbs. However the neck is fairly short and the head minuscule. But what a head! It is from the sort that only a mother could love. The tip of the snout is bent downward and the jaw is filled with numerous needle like teeth. The most bizarre aspect of the snout is that its front is split in two and armed with more teeth forming a kind of non-functional second jaw. This bizarre apparatus has been linked to a very specialized diet. The animal was probably shoveling sand at the bottom of the sea to trap small crustaceans and worms inside the cage made by its delicate teeth.

If you don’t have access to the full paper in Naturwissenshaften, go check Jaime Headden’s blog for a vivid description of the remains of this peculiar critter.

Here is the abstract of the paper:


The Luoping fauna (Anisian, Middle Triassic) is probably the oldest of Triassic faunas in Guizhou–Yunnan area, China. The reptilian assemblage is comprised of ichthyosaurs, a number of sauropterygians (pachypleurosaur-like forms), saurosphargids, protorosaurs, and archosauriforms. Here, we report on a peculiar reptile, newly found in this fauna. Its dentition is fence or comb-like and bears more than 175 pleurodont teeth in each ramus of the upper and lower jaws, tooth crown is needle-like distally and blade-shaped proximally; its rostrum strongly bends downward and the anterior end of its mandible expands both dorsally and ventrally to form a shovel-headed structure; and its ungual phalanges are hoof-shaped. The specializations of the jaws and dentition indicate that the reptile may have been adapted to a way of bottom-filter feeding in water. It is obvious that such delicate teeth are not strong enough to catch prey, but were probably used as a barrier to filter microorganisms or benthic invertebrates such as sea worms. These were collected by the specialized jaws, which may have functioned as a shovel or pushdozer (the mandible) and a grasper or scratcher (the rostrum). Our preliminary analysis suggests that the new reptile might be more closely related to the Sauropterygia than to other marine reptiles.

Reference: Cheng, L.; Chen, X.-H.; Shang, Q.-H. and Wu X.C. 2014. A new marine reptile from the Triassic of China, with a highly specialized feeding adaptation. Naturwissenschaften. In press.

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