The earliest archosaurs (Upper Permian and Lower Trias) have been classified in many different ways. All classifications introduced during the period 1945-67 are compared and then themselves classified and evaluated.

The typical characters of these archosaurs are listed. Most of them may be placed in a single suborder, the Proterosuchia, which is divided into two families, the Proterosuchidae and the Erythrosuchidae. The composition of each family is considered. Lists of genera in each family are given and of those generic names which should be regarded as nomina dubia. The placing of several genera in the synonymy of Erythrosuchus is rejected. The possible conspecificity of Chasmatosaurus vanhoepeni and C. alexanderi is considered.

A simplified scheme for the evolution of the Proterosuchia is drawn up.