Article: A primitive ichthyosaur from the Lower Triassic of British Columbia, Canada
D. B. Brinkman, Zhao Xijin and E. L. Nicholls
The primitive ichthyosaur, Grippia cf. G. longirostris occurs in Lower Triassic beds near Wapiti Lake, British Columbia. The material includes a well-preserved forelimb and a partial foot, and allows for a new interpretation of the homologies of the elements of the carpus and tarsus. Four distal carpals and five metacarpals are present in the hand, the element previously identified as the fifth distal carpal being reidentified as the fifth metacarpal. Similarly, the proximal element of the fifth digit in the foot is reidentified as the fifth metatarsal. The tarsus includes three proximal elements which are identified as an astragalus, calcaneum and centrale, four distal carpals, and five metatarsals. The centrale is lost in later ichthyosaurs. The early evolution of ichthyosaur paddles is reviewed.