Helveticosaurus

Helveticosaurus is an extinct genus of diapsid marine reptile known from the Middle Triassic (Anisian-Ladinian boundary) of southern Switzerland. It contains a single species, Helveticosaurus zollingeri, known from the nearly complete holotype T 4352 collected at Cava Tre Fontane of Monte San Giorgio, an area well known for its rich record of marine life during the Middle Triassic. Helveticosaurus is known from a nearly complete holotype which includes the premaxilla, maxilla, prefrontal, postfrontal, postorbital, squamosal, dentary and a postcranial skeleton. Several disarticulated elements are also known including teeth, portions of the snout and poscranial elements. Helveticosaurus is estimated to be about long from snout to tail. It possessed many features that were adaptations to a marine lifestyle in the shallow-sea environment that existed in Europe at the time when much of the continent was part of the Tethys Ocean. The long, flexible tail is similar to what can be seen in other extinct marine reptiles such as thalattosaurs, and it probably propelled itself through the water by means of lateral undulation. However, Helveticosaurus also possessed a robust pectoral girdle and forelimbs that were well adapted for paddle like propulsion as a supplementary method of locomotion, as seen in secondarily aquatic tetrapods. This unique combination of undulation and paddling is highly unusual for an aquatic reptile. The caniniform teeth suggest a predatory lifestyle for Helveticosaurus. Unlike most other marine reptiles which exhibited a lengthening and narrowing of the skull, the head of Helveticosaurus was more robust and boxlike. It is unknown what purpose the shortness of the skull would have had in feeding. Upon its naming and description in 1955, Helveticosaurus was classified as a member of the order Placodontia, a group of robust, barrel-bodied marine reptiles similar in lifestyle to the extant marine iguana. It was seen as a basal member of the clade, being assigned to the new family Helveticosauridae of the Helveticosauroidea superfamily.

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