A large skull of Ichthyosaurus (Reptilia: Ichthyosauria) from the Lower Sinemurian (Lower Jurassic) of Frick (NW Switzerland)

An incomplete skull of an ichthyosaur attributed to Ichthyosaurus communis Conybeare 1822 is reported from the Lower Sinemurian calcarenites (upper part of the “Beggingen Member”, previously “Arietenkalk”, Semicostatum zone) of Frick (Canton Aargau, northern Switzerland). It is the first record of this genus and species in Switzerland, and the first definite record of the genus Ichthyosaurus from central Europe. This species was hitherto only known from Lower Hettangian to Lower Sinemurian deposits of England and Upper Sinemurian sediments of Belgium. The specimen represents a particularly large individual that considerably exceeds all known English representatives of this species in skull length, and is closest in size to the single specimen from Belgium. Unusual anatomical features include a strong coossification of the posterior skull-roof bones (probably a result of an old ontogenetic age) and a very elongate and deep excavatio internasalis. A short overview of substantial Swiss Mesozoic ichthyosaur finds is provided. The Jurassic record appears very patchy so far, but has been considerably improved thanks to recent discoveries.