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The basis of this classificatory essay includes a reconsideration of the Thecodontia-Crocodylia boundaries, an evaluation of the temporal region of the thecodont skull, and some observations on the carpus, pelvis and tarsus of the group. The Proterosuchia include the Lower Triassic families Proterosuchidae-Erythrosuchidae and also the Middle and Late Triassic families Rauisuchidae and Cerritosauridae-Proterochampsidae, and the suborder is made up of two different lineages: the infraorders Rauisuchia and Proterochampsia. The Pseudosuchia is restricted to the families Euparkeriidae, Ornithosuchidae, Lagosuchidae and Scleromochlidae, with crurotarsal and mesotarsal tarsi, and short carpus. The Sphenosuchia are defined as the crocodilelike thecodonts, lightly built, with derived characters in the temporal region of the skull, elongated carpus and coracoid, and mesotarsal tarsi. The Aetosauria include the Stagonolepididae and the Doswelliidae, the latter recently described by R.E. Weems (1980) . The Phytosauria are briefly cited as it is a very well defined natural group.