Proterosuchidae


Proterosuchidae is an early, possibly paraphyletic, assemblage of basal archosauriformes 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- and σοῦχος.

Description

They were slender, medium-sized, 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.

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 take center stage as the top carnivore. Within the space of five million years the proterosuchids had evolved into a wide variety of terrestrial and semi-aquatic carnivores. The proterosuchids represent perhaps the earliest adaptive radiation of the archosaurs. They gave rise to the Erythrosuchidae some time in the Early Triassic.

Classification

Genera

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. Below is a cladogram from Ezcurra, that reexamined all historical members of the "Proterosuchia". The placement of fragmentary taxa that had to be removed to increase tree resolution are indicated by dashed lines. Taxa that are nomina dubia are indicated by the note "dubium". Bold terminal taxa are collapsed. Ezcurra recovered a monophyletic Proterosuchidae containing only Archosaurus and the species of Proterosuchus, however some species are too fragmentary to resolve whether they also fall into Proterosuchidae. Tasmaniosaurus, Fugusuchus, Sarmatosuchus, Cuyosuchus and the "Long Reef proterosuchid" on the other hand were recovered confidently outside of Proterosuchidae.