What is "proterosuchia"

Proterosuchia refers to one of the suborders of thecodontia; specifically the most primitive and ancestral forms. These were primitive, vaguely crocodile-like, archosaurs that mostly lived during the Early Triassic period.

The name Proterosuchia was coined by Robert Broom in 1906. In later classifications, several families are included, such as the Proterosuchidae, Erythrosuchidae, and Proterochampsidae.

Under the cladistic system, this is a paraphyletic grade, rather than a natural group, the name is no longer used, although it can be found in many textbooks (up to and including Carroll's Vertebrate Paleontology and Evolution)

In current phylogenetic understanding, the Proterosuchia constitute the basal Archosauriformes; that is, the archosauriform groups but excluding the true Archosauria.