The skull of a new eosuchian reptile from the Lower Jurassic of South Wales

The skull of a new fossil reptile, Gephyrosaurus bridensis gen. et sp. nov. is described. The description is based on a large collection of isolated, but well preserved skull bones from mammal-bearing fissure infills of Lower Jurassic age. The skull is diapsid with an incomplete lower temporal arcade and a fixed quadrate. Comparison with earlier non-archosaurian diapsid reptiles indicates that Gephyrosaurus is a member of the Eosuchia, an infraclass of the subclass Diapsida. The taxonomy of the Eosuchia and Squamata is discussed briefly and the use of streptostvly as a diagnostic squamate character is reviewed. Several Permian and Triassic genera, including Paliguana, Tanystropheus and Kuehneosaurus, which were previously classified as squamates, are eosuchians. Gephyrosaurus was a small insectivore with large eyes and good hearing. It was diurnal and did not compete with the contemporam mammals Morgunucodon and Kuehneolherium, which were nocturnal.