Evidence now available supports the concept of close relationship between the seymouriamorphs and diadectids, with the latter a specialized offshoot of the former. Diadectes itself clearly is not a progenitor of Chelonia. The seymouriamorphdiadectid complex may be a sterile line, except for the gephyrostegids which, originating very early among seymouriamorphs, may have led to true reptiles. There is some evidence, mostly highly tentative, that procolophons and their probable descendants, the pareiasaurs, may have arisen from the non-gephyrostegid seymouriamorph stock. Chelonia could have found their ancestery within the procolophons or pareiasaurs. If this is the case, and only additional study can confirm or deny it, then the concept of the Parareptilia, as proposed earlier (Olson, 1947), may retain much of its original meaning, with the Diadectidae, however, far removed from the ancestry of the Chelonia.