A Skull of Metriorhynchus palpebrosus in the Kimmeridgian of Normandy (Northwest France) and the Status of the Genus Metriorhynchus: The End of the Mystery?

This article provides a description of a skull assigned to Metriorhynchus palpebrosus discovered in the last century in the Upper Jurassic of Normandy. A reappraisal is made of the Upper Jurassic genus Metriorhynchus in Europe and especially of M. brevirostris (a type species of the genus), M. hastifer and M. palpebrosus, which are found in Kimmeridgian levels of France and England. A link is made to synonymize M. brevirostris with M. hastifer, thanks to a morphological autapomorphic character forgotten since 1886. It allows for the assignment of M. brevirostris, a type species of the genus, only known by an isolated snout. This interpretation permits a better understanding of this genus and, by way of the European Upper Jurassic species, a new diagnosis is proposed.