COPE  ,1 by combining the modifications of the quadrate and supporting bones with the characters used by

Huxley, further developed Owen's classification, separating the Cope . Pythonomorpha and Rhynchocephalia as distinct orders from the Lacertilia . He eventually2 elaborated the following classification, based entirely on osteological characters: I . The quadrate bone immovably fixed to the adjacent elements by suture . A . Scapular arch external to ribs; temporal region with a complex bony roof ; no longitudinal postorbital bars . A tabular and supramastoid bones and a presternum; limbs ambulatory; vertebrae amphicoelous . Order 1, COTYLOSAURIA . ,SA . Scapular arch internal to ribs; temporal region with complex roof and no longitudinal bars . A presternum; limbs ambulatory . Order 2, CHELYDO SAU RIA .