Proterosuchia is one of the suborders of the

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

group

Thecodontia Thecodontia (meaning 'socket-teeth'), now considered an obsolete taxonomic grouping, was formerly used to describe a diverse "order" of early archosaurian reptiles that first appeared in the latest Permian period and flourished until the end of t ...

, containing the most primitive and ancestral forms. These were primitive, vaguely crocodile-like, archosauriforms that mostly lived during the

Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between 251.9 Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which ...

epoch. The name Proterosuchia was coined by

Robert Broom Robert Broom Fellow of the Royal Society, FRS FRSE (30 November 1866 6 April 1951) was a British- South African medical doctor and palaeontologist. He qualified as a medical practitioner in 1895 and received his DSc in 1905 from the University ...

in 1906. In later classifications, several families were included, such as Proterosuchidae, Erythrosuchidae, and Proterochampsidae. Under the

cladistic Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...

system, this is a paraphyletic grade, rather than a natural group. The name is therefore 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 Archosauriformes (Ancient Greek, Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles encompassing Archosaur, archosaurs and some of their close relatives. It was defined by Jacques Gauthier (1994) as the clade stemmin ...

; that is, the archosauriform groups but excluding the true Archosauria.

References

{{Taxonbar, from=Q986812 Archosauriformes Paraphyletic groups Taxa named by Robert Broom