Proterosuchidae is an early family of basal

archosauriforms Archosauriformes (Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles that developed from archosauromorph ancestors some time in the Latest Permian (roughly 252 million years ago). It was defined by Jacques Gauthi ...

whose fossils are known from the Latest Permian and the Early Triassic of Europe, Asia, Africa, Australia and possibly South America. The name comes from Greek πρότερο- ("first") and σοῦχος ("

crocodile Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to inclu ...

").

Description

They were slender, medium-sized (about long, largest specimens reached ), long-snouted and superficially crocodile-like animals, although they lacked the armoured

scute A scute or scutum (Latin: ''scutum''; plural: ''scuta'' "shield") is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, and the feet of birds. The term is also used to describe the anterior po ...

s of true crocodiles, and their skeletal features are much more primitive. The limbs are short and indicate a sprawling posture, like contemporary

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

s but unlike most later archosaurs. Their most characteristic feature is a distinct down-turning of the

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...

(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

therapsid Therapsida is a major group of eupelycosaurian synapsids that includes mammals, their ancestors and relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more ...

s 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 In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic int ...

of the archosaurs. They gave rise to the

Erythrosuchidae Erythrosuchidae (meaning "red crocodiles" in Greek) are a family of large basal archosauriform carnivores that lived from the later Early Triassic (Olenekian) to the early Middle Triassic (Anisian). Naming The family Erythrosuchidae was named b ...

some time in the Early Triassic.

Classification

Genera

Phylogeny

Recent studies consider Proterosuchidae to be at least a partially

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

grouping, meaning that it does not form a true

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

with a single common ancestor and proterosuchids as its only descendants. Instead, they are a chain of successively basal archosauriforms.Ezcurra, M.D. (2016). The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. ''PeerJ'', e177

/ref> Below is a cladogram from Ezcurra (2016), that reexamined all historical members of the "Proterosuchia" (a

polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of converg ...

historical group including

proterosuchid Proterosuchidae is an early family of basal archosauriforms whose fossils are known from the Latest Permian and the Early Triassic of Europe, Asia, Africa, Australia and possibly South America. The name comes from Greek πρότερο- ("first") ...

s and

erythrosuchid Erythrosuchidae (meaning "red crocodiles" in Greek) are a family of large basal archosauriform carnivores that lived from the later Early Triassic (Olenekian) to the early Middle Triassic (Anisian). Naming The family Erythrosuchidae was named b ...

s). 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 In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

'' are indicated by the note "dubium". Bold terminal taxa are collapsed. Ezcurra (2016) recovered a monophyletic Proterosuchidae containing only ''

Archosaurus ''Archosaurus'' (meaning "ruling lizard") is an extinct genus of carnivorous proterosuchid archosauriform reptile. Its fossils are dated to the latest Permian of Russia and Poland, it is one of the earliest known archosauriforms. The type and on ...

'' and the species of ''

Proterosuchus ''Proterosuchus'' is an extinct genus of archosauriform reptiles that lived during the Early Triassic. It contains three valid species: the type species ''P. fergusi'' and the referred species ''P. alexanderi'' and ''P. goweri''. All three spec ...

'', however some species (e.g. ''

Chasmatosuchus ''Chasmatosuchus'' was an archosauriform reptile from the early Triassic period of European Russia. One of the earliest described archosauriforms, it was over 2 m long and is thought to have behaved like a modern crocodile. Its mouth had t ...

'' spp, '' Vonhuenia friedrichi'') are too fragmentary to resolve whether they also fall into Proterosuchidae. ''

Tasmaniosaurus ''Tasmaniosaurus'' ('lizard from Tasmania', although this genus is not a true lizard) is an extinct genus of archosauromorph reptile known from the Knocklofty Formation (Early Triassic) of West Hobart, Tasmania, Australia. The type species is ...

'', '' Fugusuchus'', ''

Sarmatosuchus ''Sarmatosuchus'' is an extinct genus of archosauriform reptile found in sediments of Middle Triassic age and known from the single species ''Sarmatosuchus otschevi''. It is one of the earliest stem-archosaur species known. The holotype and only ...

'', ''

Cuyosuchus ''Cuyosuchus'' is an extinct genus of archosauriform reptile. Its fossils have been found in Late Triassic-aged rocks of the Cacheuta Formation, Cuyo Basin, Mendoza, Argentina. ''Cuyosuchus'' is based on MCNAM 2669, a partial postcranial skel ...

'' and the "Long Reef proterosuchid" (SAM P41754) on the other hand were recovered confidently outside of Proterosuchidae.

References

External links

Proterosuchidae

- list of species (Mikko's Phylogeny Archive) {{Taxonbar, from=Q134278 Prehistoric reptile families Prehistoric archosauriforms Lopingian first appearances Early Triassic extinctions Taxa named by Friedrich von Huene