First description of the most complete Metriorhynchus aff. superciliosus (Thalattosuchia) specimen from the Callovian of the Vaches-Noires cliffs (Normandy, France) and limitations in the classification of Metriorhynchidae

Abstract

The metriorhynchids from the Jurassic of Normandy have been known since the 19th century. However, the remains studied until now have rarely been found in anatomical connection. The acquisition of specimen MPV 2010.3.610 that was found in the Callovian of Vaches-Noires cliffs by the Paleospace Museum in 2010, allowed the first description of the most complete Metriorhynchidae from this locality so far. The analysis of this Metriorhynchidae raises questions about the taxonomic value of several criteria currently used to distinguish between the different Callovian and Oxfordian species. The study of the cranial and postcranial elements shows that this specimen presents diagnostic criteria of different Metriorhynchidae such as the shape of the prefrontals, the mandible, the palato-maxillary suture, the atlas/axis, the cervical vertebrae as well as the extension of the jugal bone and the morphology of the teeth. A discussion highlights the limitations of the current classification of Metriorhynchidae.