Ichthyosaurs (Reptilia, Ichthyosauria) from the Lower and Middle Triassic Sulphur Mountain Formation, Wapiti Lake area, British Columbia, Canada

Abstract

Ichthyosaurs are found in the Lower and Middle Triassic members of the Sulphur Mountain Formation in the Wapiti Lake area, British Columbia. Three species are recognized: Pessosaurus sp. in the family Shastasauridae from the Middle Triassic, Mixosaurus cf. M. nordenskioeldii in the family Mixosauridae from the Lower and Middle Triassic, and Phalarodon cf. P. fraasi in the family Omphalosauridae from the Middle Triassic. Other ichthyosaur material in the Lower Triassic (Smithian) member is the oldest known from North America and coeval with the oldest known elsewhere but cannot be identified confidently at this time. This material provides new information relative to the paleobiogeography of early ichthyosaurs and additional confirmation that ichthyosaurs were already highly specialized and quite diverse by the Early Triassic.