Archosauriformes

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Archosauriformes
Temporal range: LopingianPresent, 260–0 Ma
Proterosuchus BW.jpg
Life restoration of a proterosuchid Proterosuchus fergusi
AmericanAlligator.JPG
American alligator (A. mississippiensis)
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Crocopoda
Clade: Archosauriformes
Gauthier, 1986
Subgroups

<templatestyles src="Noitalic/styles.css"/>Uatchitodon
<templatestyles src="Noitalic/styles.css"/>Erythrosuchidae
<templatestyles src="Noitalic/styles.css"/>Euparkeriidae
<templatestyles src="Noitalic/styles.css"/>Proterochampsidae
<templatestyles src="Noitalic/styles.css"/>Proterosuchidae
Crurotarsi

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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;[1] Phil Senter (2005) defined it as the most exclusive clade containing Proterosuchus and Archosauria.[2] 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, perhaps 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), who 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 archosaurs include Crocodylia, dinosaurs, birds, and a few extinct orders.

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 Ezcurra et al. (2010):[3]

Archosauriformes 

Proterosuchus




Sarmatosuchus



Fugusuchus




Osmolskina




Koilamasuchus



 Erythrosuchidae 

Shansisuchus




Vjushkovia



Erythrosuchus






Euparkeria




Chanaresuchus





Vancleavea



Doswellia



 Archosauria 

Pseudosuchia



Avemetatarsalia











Below is a cladogram from Nesbitt (2011):[4]

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.

Sources

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References

  1. 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.
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External links