Pelycosaurian reptiles have been the subject of study for over a century. The first pelycosaur found was described by LEIDY in 1854. A slab of sandstone containing part of the left side of the face of the sphenacodont Bathygnathus was discovered in Prince Edward Island, Canada, during the digging of a well. The specimen was originally identified as the lower jaw of an archosaur. Although OWEN (1876) noted the resemblance of Bathygnathusto the African therapsids, only six decades after its original description was its proper status recognized (VON HUENE 1905; CASE 1905).
