Archosauriformes

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Archosauriformes
Temporal range: LopingianPresent, 260–0 Ma
ProterosuchusDB.jpg
Life restoration of a Proterosuchus fergusi
Americanalligator.jpg
American alligator (A. mississippiensis)
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Crocopoda
Clade: Archosauriformes
Gauthier, 1986
Subgroups[2]

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[edit]

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.[2]

 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[edit]

References[edit]

  1. ^ 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. 
  2. ^ a b Ezcurra, M.D. (2016). The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. PeerJ, e1778 [1]
  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[edit]