Archosauromorpha

Archosauromorphs Temporal range: Lopingian–Present, 254.7–0 Ma PreЄ Є O S D C P T J K Pg N
Mounted skeleton of a primitive archosauromorph (Trilophosaurus buettneri)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Sauria
Clade:	Archosauromorpha von Huene, 1946
Subgroups
†Prolacerta †Choristodera †Proterosuchidae †Protorosauria †Rhynchosauria †Trilophosauria Archosauriformes Pantestudines?
Synonyms
Archelosauria?

Archosauromorpha (Greek for "ruling lizard forms") is an infraclass of diapsid reptiles that first appeared during the late Permian and became more common during the Triassic. It was defined by Jacques Gauthier, Arnold G. Kluge and Timothy Rowe (1988) as the group containing "archosaurs [i.e. Crocodylia, dinosaurs, birds, and several extinct orders] and all other saurians that are closer to archosaurs (s.s.) than they are to lepidosaurs (s.s.)" [i.e. tuataras, lizards, and snakes]. In a later publication, Michel Laurin (1991) defined Archosauromorpha as the clade containing the most recent common ancestor of Prolacerta, Trilophosaurus, Hyperodapedon and archosaurs and all its descendants; David Dilkes (1998) formulated a more inclusive definition of Archosauromorpha, defining it as the clade containing Protorosaurus and all other saurians that are more closely related to Protorosaurus than to Lepidosauria.

Included in this infraclass are the groups Rhynchosauria, Trilophosauridae, Prolacertiformes and Archosauriformes. While superficially these reptiles vary in appearance (at one time they were even included in different subclasses – the trilophosaurs were considered euryapsids and the rhynchosaurs were considered lepidosaurs and were included in the same order as the tuatara), they are actually united by a number of small skeletal and skull-related details that suggest they form a clade that descended from a single common ancestor. Additional groups with uncertain phylogenetic position that are included in Archosauromorpha by some authors (and excluded from it by others) are Choristodera, drepanosaurs, thalattosaurs, ichthyopterygians, sauropterygians and turtles.

Of the taxa mentioned above, rhynchosaurs, trilophosaurs and prolacertiforms died out at or before the end-Triassic extinction. The choristoderans continued as a minor group until the Miocene, and the Archosauriformes were important factors in early Triassic environments before giving rise to the even more successful Archosauria.

Phylogeny

Below is a cladogram modified from the analysis by Sues (2003). It was provided with the original description of Teraterpeton. Like in other recent analyses, Prolacertiformes was recovered as polyphyletic, and was therefore replaced by Protorosauria.

Lepidosauromorpha  Archosauromorpha   Choristodera  Lazarussuchus Champsosaurus Cteniogenys  Protorosauria  Protorosaurus  Drepanosauridae  Drepanosaurus Megalancosaurus  Tanystropheidae  Macrocnemus Langobardisaurus Tanystropheus  Trilophosauria  Teraterpeton Trilophosaurus  Rhynchosauria  Mesosuchus Howesia Rhynchosaurus Stenaulorhynchus Teyumbaita Hyperodapedon Prolacerta  Archosauriformes  Proterosuchus Euparkeria

The cladogram shown below follows the most likely result found by an analysis of turtle relationships using both fossil and genetic evidence by M.S. Lee, in 2013.

	Lepidosauromorpha  Archosauromorpha (=Archelosauria)  †Choristodera †Trilophosaurus †Rhynchosauria Archosauriformes  Pantestudines  †Eosauropterygia †Placodontia †Sinosaurosphargis †Odontochelys  Testudinata  †Proganochelys Testudines

External links

• palaeos
• Paleofiles – lists taxa