Pseudosuchia

Pseudosuchians Temporal range: Ma[1] PreꞒ Ꞓ O S D C P T J K Pg N
Aetosauria )
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauria
Clade:	Pseudosuchia Zittel, 1887
Subgroups
†Dasygnathoides † Phytosauria ? †Ornithosuchidae Suchia
Synonyms
Crocodylotarsi Benton & Clark, 1988[2]

Pseudosuchia (from

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. By this time, Pseudosuchia had also been defined as a clade, but it was not widely embraced until 2011.

In 2011 paleontologist Sterling Nesbitt proposed that Crurotarsi, as it was then defined, must include not only crocodilian-line archosaurs, but all other archosaurs including birds, non-avian dinosaurs, and pterosaurs.^[4] The clade Pseudosuchia as originally defined could still be used to identify crocodilian-line archosaurs, and since many recent studies support Nesbitt's findings, Pseudosuchia is again commonly used.

Taxonomic history

The name Pseudosuchia was coined by Karl Alfred von Zittel in 1887–1890 to include three taxa (two aetosaurs and Dyoplax) that were superficially crocodilian-like, but were not actually crocodilian. Hence the name "false crocodiles".

In mid-20th century textbooks, like

Pseudosuchians appeared during the late Olenekian (early Triassic); by the Ladinian (late Middle Triassic) they dominated the terrestrial carnivore niches. Their heyday was the Late Triassic, during which time their ranks included erect-limbed rauisuchians, herbivorous armored aetosaurs, the large predatory poposaurs, the small agile sphenosuchian crocodilians, and a few other assorted groups.

The

As the Mesozoic progressed, the Protosuchia gave rise to more typically crocodile-like forms. While dinosaurs were the dominant animals on land, the crocodiles flourished in rivers, swamps, and the oceans, with far greater diversity than they have today. With the end-Cretaceous extinction, the dinosaurs became extinct, with the exception of the birds, while the crocodilians continued with little change. Today, the crocodiles, alligators, and gharials are the surviving representatives of this lineage.

Interestingly, the Mesozoic range of cranial disparity is higher than the Triassic one, suggesting crocodylomorphs attained a high degree of diversification compared to Triassic pseudosuchians.^[8]

Phylogeny

Pseudosuchia was defined as a stem-based clade in 1985.

Archosauriformes

†Proterosuchidae †Erythrosuchus †Vancleavea †Proterochampsia †Euparkeria  Crurotarsi  † Phytosauria   Archosauria   Avemetatarsalia (bird-lineage of archosaurs)  Pseudosuchia †Ornithosuchidae  Suchia  †Gracilisuchus †Turfanosuchus †Revueltosaurus † Aetosauria †Ticinosuchus  Paracrocodylomorpha  †Poposauroidea  Loricata  †Prestosuchus †Saurosuchus †Batrachotomus †Fasolasuchus †Rauisuchidae Crocodylomorpha (crocodilian‑lineage of archosaurs)

The following cladogram is from a slightly older study, Brusatte, Benton, Desojo and Langer (2010).

, the retention of phytosaurs within Pseudosuchia, and a close relation between aetosaurs and crocodylomorphs, replicate the results of older studies. However, the findings of Nesbitt (2011) have been more widely supported by pseudosuchian-focused analyses published since 2011.

†Erythrosuchus †Euparkeria †Proterochampsidae   Archosauria   Avemetatarsalia Pseudosuchia / Crurotarsi  † Phytosauria  Suchia  † Aetosauria  Paracrocodylomorpha  †Gracilisuchus  Bathyotica  †Erpetosuchus Crocodylomorpha †Revueltosaurus †Ornithosuchidae  Rauisuchia  †Poposauroidea   Rauisuchoidea   †Arganasuchus †Fasolasuchus' †Stagonosuchus †Ticinosuchus †Rauisuchidae  Prestosuchidae  †Saurosuchus †Batrachotomus †Prestosuchus

References