Gephyrosaurus

Did You Know?

• Gephyrosaurus is suggested to have been an insectivore that was probably diurnal.
• Its postcranial skeleton suggests it was agile and capable of climbing.
• Numerous jaw bones with healed fractures indicate it may have fought with conspecifics over territory.

Description

Gephyrosaurus bridensis had a skull roughly 3 cm long, 2 cm wide and 1 cm deep. The skull lacks a complete temporal bar, with a gap between the jugal and quadrate bones. Unlike more advanced sphenodontian rhynchocephalians, it retains a reduced lacrimal bone. The frontal and parietal bones are unpaired. Each jaw half bears about 35–40 teeth, all pleurodont, attached to a shelf on the inner side of the jaw. Teeth at the back have shallow roots and slower replacement than those at the front. The postcranial skeleton was lizard-like with long legs.

Taxonomy

The type species Gephyrosaurus bridensis was named by Susan E. Evans in 1980 from Early Jurassic fissure fill deposits in South Wales. A second species, G. evansae, was described in 2017 from a maxilla in Late Triassic (Rhaetian) fissure fills of Somerset; it differs by having smaller, more pointed, and more densely packed teeth. Originally placed in the non-monophyletic group "Eosuchia", Gephyrosaurus is now generally considered among the most primitive rhynchocephalians, outside Sphenodontia. Some authors instead find it more closely related to Squamata. Evans placed it in its own family, Gephyrosauridae, later expanded to include other genera.