A new species of Shastasaurus (Reptilia: Ichthyosauria) from the Triassic of British Columbia: the most complete exemplar of the genus

ABSTRACT

At least six species of Shastasaurus have been described in the literature and accounts of its anatomy, which have included a restoration of the entire skeleton, give the impression that it is a well understood genus. This is not the case. Most of the species, primarily from California, were erected on inadequate material—especially vertebrae and rib fragments—and should be considered nomina dubia. Although there is information for the skull, fins, and girdles, most of the material is incomplete. Thus there is no complete skull, forefin or hindfin, nor is the vertebral column known much beyond the pelvic girdle.

A partial skeleton of Shastasaurus, from the Upper Triassic of Williston Lake, British Columbia, is the most complete specimen known to date. It is described here as a new species, Shastasaurus neoscapularis. Being early Norian in age, it is geologically younger, by some 5–12 Ma, than the other material of Shastasaurus, which is late Carnian. While similar to the older material in other respects, the new material differs in having a radically different scapula, which is like that of typical Jurassic taxa such as Ichthyosaurus and Stenopterygius. The skull, with its large orbit, narrow postorbital region, and small maxilla is also like that of a Jurassic ichthyosaur. As comparative data are unavailable, it is not known whether these cranial features are typical of the genus or only of the new species.