First complete forefin of the ichthyosaur Grippia longirostris from the Triassic of Spitsbergen

A new and nearly complete forefin has been discovered on a slab containing a specimen of the ichthyosaur Grippia longirostris. It is the only well-articulated forefin of this poorly known species, and is one of the most complete forefins known for the earliest ichthyosaurs from the Lower Triassic (Spathian). Contrary to the proposals of previous authors, the terminal phalanges did not support 'hooves'. The forefin resembles that of Utatsusaurus hataii, another Spathian ichthyosaur, but is more derived, sharing four synapomorphies with Mixosaurus cornalianus, a slightly younger ichthyosaur from the Middle Triassic. Ichthyosaurian forefins, described from British Columbia and assigned to Grippia, lack at least two of these synapomorphies, and thus do not belong to this genus. A 'partial hindfin' of Grippia, also from British Columbia, is similar to the new forefin, casting doubt on its identification as a hindfin.