Gephyrosaurus is a genus of early Rhynchocephalia first described and named in 1980 by Susan E. Evans.They are distantly related to the extant Sphenodon (tuatara of New Zealand) with which they shared a number of skeletal features including a large tooth row along the side of the palatine bone (part of the palate) and posterior process of the dentary bone (part of the lower jaw). They lived during Early Jurassic in Wales, UK.The primitive cranial features of this organism places it within the order of Eosuchia.