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Proterosuchids Temporal range: Latest Permian to Latest Early Triassic, 252–247 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓ Possible Middle Triassic records
Restored skull of Archosaurus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauromorpha
Clade:	Archosauriformes
Family:	†Proterosuchidae Huene, 1914
Genera
Proterosuchus ?Koilamasuchus ?Sarmatosuchus ?Blomosuchus ?Ankistrodon Chasmatosuchinae Vonhuenia Jaikosuchus Gamosaurus Chasmatosuchus Tsylmosuchus Samsarasuchus Archosaurus
Synonyms
Proterosuchinae Huene, 1914 Chasmatosauridae Haughton, 1924 Chasmatosaurinae Haughton, 1924 Pelycosimiidae Abel, 1919

Proterosuchidae is an early family of basal archosauriforms whose fossils are known from the Late Permian and the Early Triassic. The highest diversity of genera is known from European Russia, but fossils are also known from South Africa, India, China, Australia, Brazil and possibly Argentina. The name comes from Greek πρότερο- ("first") and σοῦχος ("crocodile").

Description

They were slender, medium-sized (about 1.5 m (4 ft 11 in) long, largest specimens reached 3.5–4 m (11–13 ft)), long-snouted and superficially crocodile-like animals, although they lacked the armoured scutes of true crocodiles, and their skeletal features are much more primitive. The limbs are short and indicate a sprawling posture, like contemporary lizards but unlike most later archosaurs.

Their most characteristic feature is a distinct down-turning of the premaxilla (the front of the upper jaw, which overhangs the lower jaw).

Evolutionary history

The terminal Permian catastrophe, which killed off 95% of all types of life, cleared the world of all large therapsids and allowed the proterosuchids to become the top predators. Within the space of five million years the proterosuchids had evolved to fill a wide variety of terrestrial and semi-aquatic niches. The proterosuchids represent perhaps the earliest adaptive radiation of the archosaurs. They gave rise to the Erythrosuchidae some time in the Early Triassic.

A 2023 study recovered a majority of proterosuchids outside of Proterosuchus and Sarmatosuchus as belonging to a distinct subfamily, the Chasmatosuchinae, defined as "the most inclusive clade containing Chasmatosuchus rossicus, but not Proterosuchus fergusi, "Chasmatosaurus" yuani, Proterosuchus alexanderi, Proterosuchus goweri, Erythrosuchus africanus, or Alligator mississippiensis (the American alligator)". Chasmatosuchinae contains many Triassic proterosuchids in addition to the only Permian proterosuchid, Archosaurus; this would suggest that an initial taxonomic diversification of the Proterosuchidae (including an initial taxonomic divergence between Proterosuchus and chasmatosuchines) had already occurred in the Permian.

Classification

Phylogeny

Recent studies consider Proterosuchidae to be at least a partially paraphyletic grouping, meaning that it does not form a true clade with a single common ancestor and proterosuchids as its only descendants. Instead, they are a chain of successively basal archosauriforms. Proterosuchidae sensu stricto is defined as "all taxa more closely related to Proterosuchus fergusi than to Erythrosuchus africanus, Crocodylus niloticus (the Nile crocodile), or Passer domesticus (the house sparrow). 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. Ezcurra (2016) recovered a monophyletic Proterosuchidae containing only Archosaurus and the species of Proterosuchus, however some species (e.g. Chasmatosuchus spp, Vonhuenia friedrichi) are too fragmentary to resolve whether they also fall into Proterosuchidae. Tasmaniosaurus, Fugusuchus, Sarmatosuchus, Cuyosuchus and the "Long Reef proterosuchid" (SAM P41754) on the other hand were recovered confidently outside of Proterosuchidae.

The following phylogeny for the Proterosuchidae sensu stricto was recovered by Ezcurra et al (2023):

Genera

Genus	Status	Age	Location	Description	Images
Ankistrodon	nomen dubium	Early Triassic	India
Archosaurus	Valid	Late Permian, Changhsingian	Russia
Blomosuchus	nomen dubium	Early Triassic, Induan	Russia
Chasmatosuchus	Valid	Early Triassic	Russia
Gamosaurus	Valid	Early Triassic	Russia
Jaikosuchus	Valid	Early Triassic	Russia
Koilamasuchus	Disputed	Middle - Late Triassic	Argentina
Proterosuchus	Valid	Early Triassic	South Africa
Samsarasuchus	Valid	Early Triassic	India
Sarmatosuchus	Disputed	Early Triassic	Russia
Tsylmosuchus	Valid	Early Triassic	Russia
Vonhuenia	Valid	Early Triassic, Induan	Russia

References

1. ^ Ezcurra, Martín D.; Bandyopadhyay, Saswati; Sengupta, Dhurjati P.; Sen, Kasturi; Sennikov, Andrey G.; Sookias, Roland B.; Nesbitt, Sterling J.; Butler, Richard J. (25 October 2023). "A new archosauriform species from the Panchet Formation of India and the diversification of Proterosuchidae after the end-Permian mass extinction". Royal Society Open Science. 10 (10). Bibcode:2023RSOS...1030387E. doi:10.1098/rsos.230387. ISSN 2054-5703. PMC 10598453. PMID 37885992.
2. Julia Brenda Desojo, Randall B. Irmis, Sterling J. Nesbitt (2013). Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and Their Kin. Geological Society. p. 20. ISBN 9781862393615. Retrieved 14 September 2022.{{cite book}}: CS1 maint: multiple names: authors list (link)
3. "Archosauria: Archosauriformes". Palaeos. Retrieved 29 October 2014.
4. 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. Bibcode:2010JVPal..30.1433E. doi:10.1080/02724634.2010.501446. S2CID 83826840.
5. ^ Ezcurra, M.D. (2016). The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. PeerJ, e1778

Further reading

• Benton, M. J. (2000), Vertebrate Paleontology, 2nd Ed.; (2004) 3rd edition Blackwell Science Ltd
• Carroll, R. L. (1988), Vertebrate Paleontology and Evolution, WH Freeman & Co.

External links

• Proterosuchidae
• Proterosuchidae - list of species (Mikko's Phylogeny Archive)

v t e Archosauromorpha
Kingdom: Animalia Phylum: Chordata Class: Sauropsida Clade: Diapsida Clade: Sauria Clade: Archelosauria Sauropsida see Sauropsida Archosauromorpha see below↓
Archosauromorpha Archosauromorpha †Aenigmastropheus †Czatkowiella †Elachistosuchus? †Elessaurus †Malutinisuchus †Mecistotrachelos †Prolacertoides †Protorosaurus †Rhombopholis †Vritramimosaurus †Tanysauria Jesairosaurus? Trachelosauridae Austronaga Dinocephalosaurus Fuyuansaurus? Gracilicollum? Protanystropheus Pectodens Sclerostropheus? Trachelosaurus Sharovipterygidae? Ozimek Sharovipteryx Tanystropheidae Amotosaurus Augustaburiania Cosesaurus Fuyuansaurus? Gracilicollum? Gwyneddosaurus Langobardisaurus Luxisaurus Macrocnemus Raibliania Sclerostropheus? Tanystropheus Tanytrachelos Sharovipterygidae? Crocopoda †Boreopricea †Cryptovaranoides? †Tasmaniosaurus †Teyujagua †Allokotosauria see Allokotosauria †Rhynchosauria see Rhynchosauria †Prolacertidae? Kadimakara Prolacerta Archosauriformes see below↓
Archosauriformes Archosauriformes †Antarctanax †Cuyosuchus †Eorasaurus? †Kalisuchus †Koilamasuchus †Sarmatosuchus †Syntomiprosopus †Proterosuchidae Archosaurus Chasmatosuchus? Gamosaurus Jaikosuchus Proterosuchus Samsarasuchus Tsylmosuchus? Vonhuenia? †Protopyknosia Kranosaura Triopticus †Erythrosuchidae Bharitalasuchus Chalishevia Erythrosuchus Fugusuchus? Garjainia Guchengosuchus Shansisuchus Uralosaurus Eucrocopoda †Asperoris †Dorosuchus †Heteropelta †Litorosuchus †Marcianosuchus †Polymorphodon †Vancleavea †Euparkeriidae Euparkeria Halazhaisuchus Osmolskina †Proterochampsia see Proterochampsia Crurotarsi †Phytosauria see Phytosauria Archosauria Incertae sedis †Sikannisuchus? †Smok Avemetatarsalia see Avemetatarsalia includes birds Pseudosuchia see Pseudosuchia includes crocodilians
Related topics Tooth taxa †Crosbysaurus †Lucianosaurus †Tecovasaurus †Palaeosaurus †Protecovasaurus †Uatchitodon †Zanclodon Nomina dubia †Albisaurus †Ankistrodon †Avipes †Blomosuchus †Collilongus †Exilisuchus †Fenhosuchus †Megacnemus †Microcnemus †Vjushkovisaurus †Wangisuchus Paraphyletic groups Proterosuchia Protorosauria Thecodontia Possible members Choristodera Drepanosauromorpha Kuehneosauridae Ichthyosauromorpha Sauropterygia Thalattosauria
Category

• Proterosuchids
• Prehistoric reptile families
• Lopingian first appearances
• Early Triassic extinctions
• Taxa named by Friedrich von Huene