Proterosuchidae is an early family of

basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...

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") and σοῦχος ("

crocodile Crocodiles (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 include all extant ...

").

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 al ...

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 ...

(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 mor ...

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 by ...

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 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 conver ...

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 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'' and the species of '' Proterosuchus'', however some species (e.g. '' Chasmatosuchus'' spp, ''

Vonhuenia friedrichi ''Vonhuenia'' (named after Friedrich von Huene) is an extinct genus of basal archosauriform from the Early Triassic of Russia. Fossils have been found in the Vokhminskaya Formation, along the Vetluga River that are Induan in age, making ''Vo ...

'') are too fragmentary to resolve whether they also fall into Proterosuchidae. '' Tasmaniosaurus'', ''

Fugusuchus ''Fugusuchus'' is an extinct genus of archosauriform, probably the basal-most member of the family Erythrosuchidae. The genus is known from a single fossil from the middle Early Triassic Heshanggou Formation in Shanxi, China. The partial skelet ...

'', '' Sarmatosuchus'', '' Cuyosuchus'' 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