Thalattosaurus

Thalattosaurus (pron.:"tha-la-to-SORE-us") meaning "ocean lizard" is an extinct genus of marine reptile in the family Thalattosauridae. They are aquatic diapsids that are known exclusively from the Triassic period, and have recently gained attention as a result of studies on general diapsid phylogeny.[1]

Thalattosaurus was a shellfish-eating reptile around 2 meters (7 ft) in length occurring in the Lower and Middle of British Columbia as well as Upper Triassic of California.[2]

Although originally described as four distinct species by Merriam in 1905, one was proven to be T. alexandrae upon further inspection and another has a missing type specimen. Currently it is believed to include two known species; Thalattosauridae alexandrae and Thalattosauridae borealis.

Both species have paddle-like limbs and a down-turned rostrum.

Etymology
Thalattosaurus alexandrae was named by Merriam in 1904, Thallattosaurus meaning "ocean lizard" and alexandrae in honor of Annie Alexander, an amateur paleontologist and patron to the University of California Museum of Paleontology.[3] Thalattosaurus borealis was named after its Northern appearance, with Thalattosaurus meaning "ocean lizard" and borealis coming from boreas (Greek word, βορέας) meaning "Northern."

Thalattosauroidea (which contains Clarazia and Thalattosaurus) have a relatively short rostrum, distinct from the elongate primitive condition, with convergent lateral margins that terminate in a pointed tip. It is also characteristic of their supratemporal to contact the frontal bone, having a heavy postorbital bar, diastema present that separates the premaxillary from the maxillary teeth, and a deep lower jaw. The Thalattosauroidea are easily distinguished by the their down-turned snouts. In Clarazia and Thalattosaurus, the snouts taper to a narrow tip, with the premaxilla at the tip down-turned.

Geology and environment
Range: Early/middle (Olenekian/Anisian) to Late (Carnian) Triassic in a marine; shale and marl environment. Probably feeding on shelled animals. The Sulphur Mountain Formation consists of a series of marine siltstones, silty limestones, and fine gained sandstones. All of the thalattosaur specimens from Wapiti Lake are preserved in sandstones, suggestive of shallow water conditions. Thalattosaur limbs are not paddle-like, but Thalattosaurus limbs are.

Thalattosaurus alexandrae was about six feet long and an excellent swimmer.[5] T. alexandrae probably had a long flattened tail and claws possibly used to withstand the force of the surf when crawling up on shore.[6] It is likely that they often spent their time near the shore instead of deep-sea, open-water environments.

Since all of the known fossils come from Triassic and British Columbia (or one from California) it can be assumed that they were limited in both space and time.