Rauisuchia

"Rauisuchians" Temporal range: Triassic, 249–200 Ma Descendant taxon Crocodylomorpha survives to present; and possible early Jurassic presence.[1] PreꞒ Ꞓ O S D C P T J K Pg N
Mounted skeleton of Prestosuchus chiniquensis (a basal loricatan) in the American Museum of Natural History.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauria
Clade:	Pseudosuchia
Clade:	Suchia
Informal group:	†Rauisuchia Huene, 1942
Groups included
Poposauroidea Rauisuchidae Prestosuchidae
Cladistically included but traditionally excluded taxa
Crocodylomorpha

"Rauisuchia" is a paraphyletic group of mostly large and carnivorous Triassic archosaurs.^[2] Rauisuchians are a category of archosaurs within a larger group called Pseudosuchia, which encompasses all archosaurs more closely related to crocodilians than to birds and other dinosaurs. First named in the 1940s, Rauisuchia was a name exclusive to Triassic archosaurs which were generally large (often 4 to 6 metres (13 to 20 ft)), carnivorous, and quadrupedal with a pillar-erect hip posture, though exceptions exist for all of these traits. Rauisuchians, as a traditional taxonomic group, were considered distinct from other Triassic archosaur groups such as early dinosaurs, phytosaurs (crocodile-like carnivores), aetosaurs (armored herbivores), and crocodylomorphs (lightly-built crocodilian ancestors).^[3]

However, more recent studies on archosaur evolution have upended this idea based on phylogenetic analyses and cladistics, a modern approach to taxonomy based on clades (nested monophyletic groups of common ancestry). Since the early 2010s, archosaur classification schemes have stabilized on a system where Rauisuchia is rendered an evolutionary grade, or even a wastebin taxon. Crocodylomorphs most likely originated from a rauisuchian ancestor based on a myriad of shared traits, and some "rauisuchians" (such as Postosuchus and Rauisuchus) appear to be more closely related to crocodylomorphs than to other "rauisuchians" (such as Prestosuchus and Saurosuchus).^[2]

As a result, Rauisuchia in its traditional usage may be considered paraphyletic: a group which is defined by shared ancestry but also excludes a descendant taxon (in this case, crocodylomorphs). To designate it as an informal group in scientific literature, the name is often enclosed in quotation marks.^[2] Several monophyletic groups have been erected to classify "rauisuchians" in a cladistic framework. The closest concept is the clade Paracrocodylomorpha, which includes most "rauisuchian" taxa and their crocodylomorph descendants. Paracrocodylomorpha is divided into two branches: Poposauroidea, which includes a variety of strange "rauisuchians" (some of which were bipedal and/or herbivorous) and Loricata, which includes most typical "rauisuchians" and crocodylomorphs.^[2]