Archosauriformes

Archosauriformes Temporal range: Lopingian–Present, 260–0 Ma PreЄ Є O S D C P T J K Pg N
Life restoration of a Proterosuchus fergusi
American alligator (A. mississippiensis)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Crocopoda
Clade:	Archosauriformes Gauthier, 1986
Subgroups[1]
†Cuyosuchus †Eorasaurus †Fugusuchus †Kalisuchus †Sarmatosuchus †Proterosuchidae †Erythrosuchidae Eucrocopoda Ezcurra, 2016 †Asperoris †Dongusuchus †Dorosuchus †Yarasuchus †Euparkeriidae[2] †Proterochampsia Archosauria

Archosauriformes (Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles that developed from archosauromorph ancestors some time in the Late Permian (roughly 250 million years ago). It was defined by Jacques Gauthier (1994) as the clade stemming from the last common ancestor of Proterosuchidae and Archosauria;^[3] Phil Senter (2005) defined it as the most exclusive clade containing Proterosuchus and Archosauria.^[4] These reptiles, which include members of the family Proterosuchidae and more advanced forms, were originally superficially crocodile-like predatory semi-aquatic animals about 1.5 meters (5 ft) long, with a sprawling elbows-out stance and long snouts. Unlike the bulk of their therapsid contemporaries, the proterosuchids survived the catastrophe at the end of the Permian, perhaps because they were opportunistic scavengers or because they could retreat into water to find respite from an overheated climate. Any such scenarios are hypothetical; what is clearer is that these animals were highly successful in their new environment, and evolved quickly. Within a few million years at the opening of the Triassic, the proterosuchids had given rise to the Erythrosuchidae (the first sauropsids to totally dominate their environment), which in turn were the ancestors of the small agile Euparkeriidae, from which a number of successfully more advanced families – the archosaurs proper – evolved rapidly to fill empty ecological niches in the devastated global system. The Archosauria includes crocodylians, birds, and their extinct relatives.

Pre-Euparkeria Archosauriformes have previously been included in the suborder Proterosuchia of the order Thecodontia. Under the cladistic methodology, Proterosuchia has been rejected as a paraphyletic assemblage, and the pre-archosaurian taxa are simply considered as basal Archosauriformes.

Relationships

Below is a cladogram from Nesbitt (2011):^[5]

Archosauriformes	Proterosuchidae  Archosaurus Proterosuchus Erythrosuchus Vancleavea  Proterochampsia  Tropidosuchus Chanaresuchus Euparkeria  Crurotarsi   Phytosauria*  Parasuchus Smilosuchus Pseudopalatus  Archosauria  Pseudosuchia Avemetatarsalia *Note: Phytosaurs were previously placed within Pseudosuchia, or crocodile-line archosaurs.

Below is a cladogram from Ezcurra (2016), that reexamined all historical members of the "Proterosuchia" (a polyphyletic historical group including proterosuchids and erythrosuchids). The placement of fragmentary taxa that had to be removed to increase tree resolution are indicated by dashed lines (in the most derived position that they can be confidently assigned to). Taxa that are nomina dubia are indicated by the note "dubium". Bold terminal taxa are collapsed.^[1]

Crocopoda

Allokotosauria Rhynchosauria Boreopricea funerea Prolacertidae SAM-PK-591 "Ankistrodon indicus" (dubium) "Blomosuchus georgii" (dubium) Tasmaniosaurus triassicus  Archosauriformes   Chasmatosuchus  Chasmatosuchus magnus Chasmatosuchus rossicus Gamosaurus lozovskii Chasmatosuchus vjushkovi Vonhuenia friedrichi Proterosuchidae Eorasaurus olsoni Kalisuchus rewanensis Fugusuchus hejiapanensis Sarmatosuchus otschevi Cuyosuchus huenei Erythrosuchidae  Eucrocopoda  Asperoris mnyama Dorosuchus neoetus Euparkeria capensis Dongusuchus efremovi Yarasuchus deccanensis  Proterochampsia  Doswelliidae Proterochampsidae  Archosauria  Avemetatarsalia  Pseudosuchia  Phytosauria The rest of Pseudosuchia

Sources

• Gauthier, J. A. (1986). "Saurischian monophyly and the origin of birds". In Padian, K. (ed.). The Origin of Birds and the Evolution of Flight. Memoirs of the California Academy of Sciences 8. California Academy of Sciences. pp. 1–55. ISBN 0-940228-14-9. External link in |title= (help)
• Gauthier, J. A.; Kluge, A. G.; Rowe, T. (June 1988). "Amniote phylogeny and the importance of fossils". Cladistics (John Wiley & Sons) 4 (2): 105–209. doi:10.1111/j.1096-0031.1988.tb00514.x.

References

1. Ezcurra, M.D. (2016). The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. PeerJ, e1778
2. Sookias, R. B.; Sullivan, C.; Liu, J.; Butler, R. J. (2014). "Systematics of putative euparkeriids (Diapsida: Archosauriformes) from the Triassic of China". PeerJ 2: e658. doi:10.7717/peerj.658. PMC 4250070. PMID 25469319.
3. Gauthier J. A. (1994): The diversification of the amniotes. In: D. R. Prothero and R. M. Schoch (ed.) Major Features of Vertebrate Evolution: 129-159. Knoxville, Tennessee: The Paleontological Society.
4. Phil Senter (2005). "Phylogenetic taxonomy and the names of the major archosaurian (Reptilia) clades". PaleoBios 25 (2): 1–7.
5. Nesbitt, S.J. (2011). "The early evolution of archosaurs: relationships and the origin of major clades" (PDF). Bulletin of the American Museum of Natural History 352: 1–292. doi:10.1206/352.1.

External links

• Paleos
• Mikko's Phylogeny Archive