Archosauriformes

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Archosauriformes
Temporal range: Lopingian - Present, 260–0Ma
Euparkeria BW.jpg
Life restoration of Euparkeria capensis
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Clade: Archosauriformes
Gauthier, 1986
Subgroups

Uatchitodon
Erythrosuchidae
Euparkeriidae
Proterochampsidae
Proterosuchidae
Crurotarsi

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[edit]

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.

Literature[edit]

References[edit]

  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.
  2. ^ Phil Senter (2005). "Phylogenetic taxonomy and the names of the major archosaurian (Reptilia) clades". PaleoBios 25 (2): 1–7. 
  3. ^ Ezcurra, M.D.; Lecuona, A.; Martinelli, A. (2010). "A new basal archosauriform diapsid from the Lower Triassic of Argentina". Journal of Vertebrate Paleontology 30 (5): 1433–1450. doi:10.1080/02724634.2010.501446. 
  4. ^ Nesbitt, S.J. (2011). "The early evolution of archosaurs: relationships and the origin of major clades". Bulletin of the American Museum of Natural History 352: 1–292. doi:10.1206/352.1. 

External links[edit]