[2] Unlike more advanced rhynchocephalians belonging to Sphenodontia,[3] Gephyrosaurus bridensis retains a lacrimal bone in the skull, though it is considerably reduced in size compared to more primitive reptiles.

[1] The type species G. bridensis was described by Susan E. Evans in 1980 based on fossils found in Early Jurassic fissure fill deposits in South Wales.

[2] In 2017 a second species G. evansae was described from a maxilla found in fissure fill deposits from the Late Triassic (Rhaetian) of nearby Somerset.

[5] When originally described, Gephyrosaurus was placed in "Eosuchia",[1][2] which is now considered to be a non-monophyletic group that included a wide variety of unrelated small diapsid reptiles.

Findings of numerous jaw bones with healed fractures suggests that Gephyrosaurus may have engaged in fights with other conspecifics over territory, as occurs in some modern lizards.