Some cases of fused and concrescentexocranial bones in the Lower Permian seymouriamorph Tetrapod Discosauriscus Kuhn; 1933

An example of a parietal fused with an intertemporal and an example of concrescence of a parietal with an extra intertemporal in the metamorphic stages of the Lower Permian seymouriamorph are described. It is concluded that it is necessary to take account of phylogenetic fusion of two or more original components in the formation of the skull roofing bones in different phylogenetic lines of vertebrates ; and use this information when identifying homologous bones in various early tetrapod groups.