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The name Crurotarsi is derived from the Latin word crus (lower leg) and the Greek word tarsos (ankle). It refers to the specialized articulation (a crurotarsal joint) between the lower leg (specifically the fibula ) and the ankle (specifically the calcaneum ) which is present in the skeletons of reptiles such as suchians and phytosaurs .
The name Pseudosuchia was originally given to a group of superficially crocodile-like prehistoric reptiles from the Triassic period, but fell out of use in the late 20th century, especially after the name Crurotarsi was established in 1990 to label the clade (evolutionary grouping) of archosaurs encompassing most reptiles previously identified as pseudosuchians.
Suchia is a clade of archosaurs containing the majority of pseudosuchians (crocodilians and their extinct relatives). It was defined as the least inclusive clade containing Aetosaurus ferratus, Rauisuchus tiradentes, Prestosuchus chiniquensis, and Crocodylus niloticus (the living Nile crocodile) by Nesbitt (2011). [1]
The lower edge of the lateral (outer) side of the jaw was covered in small longitudinal grooves, a feature seemingly unique to Nundasuchus among early archosaurs. Less unusual is the presence of several rows of pits on the lateral surface and large grooves on the medial surface.
The thin tibia and fibula (lower leg bones) of aphanosaurs do not possess unique traits to the same extent as the femur. However, they are also shorter than the femur. These proportions are rare among early avemetatarsalians, but more common among pseudosuchians and non-archosaur archosauriformes.
Prestosuchus (meaning "Prestes crocodile") is an extinct genus of pseudosuchian in the group Loricata, which also includes Saurosuchus and Postosuchus.It has historically been referred to as a "rauisuchian", and was the defining member of the family Prestosuchidae, though the validity of both of these groups is questionable: Rauisuchia is now considered paraphyletic and Prestosuchidae is ...
"Rauisuchia" is a paraphyletic group of mostly large and carnivorous Triassic archosaurs. [2] Rauisuchians are a category of archosaurs within a larger group called Pseudosuchia, which encompasses all archosaurs more closely related to crocodilians than to birds and other dinosaurs.
Poposauroidea was a diverse group of pseudosuchians, containing genera with many different ecological adaptations. Some (Poposaurus and shuvosaurids) were short-armed bipeds, while others (ctenosauriscids and Lotosaurus) were robust quadrupeds with elongated neural spines, creating a 'sail' like that of certain "pelycosaurs" (like Dimetrodon) and spinosaurids.