Pseudosuchia

Pseudosuchians
Temporal range:
Early Triassic–Present, 248–0 Ma[1]
Postosuchus (Rauisuchidae) and Desmatosuchus (Aetosauria)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Zittel, 1887
Subgroups
Synonyms
  • Crocodylotarsi Benton & Clark, 1988[2]

Pseudosuchia (from Greek: ψεύδος (pseudos), "false" and Greek: σούχος (souchos), "crocodile")[3] is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely related to crocodilians than to birds. Pseudosuchians are also informally known as "crocodilian-line archosaurs", in contrast to the "bird-like archosaurs" or Avemetatarsalia. Despite Pseudosuchia meaning "false crocodiles", the name is a misnomer as true crocodilians are now defined as a subset of the group.

The clade Pseudosuchia is potentially equivalent to Crurotarsi even though the latter has a different, node-based definition: "all taxa the least inclusive clade containing Rutiodon carolinensis (Emmons, 1856), and Crocodylus niloticus (Laurenti, 1768)." However, a major 2011 study of Triassic archosaur relations proposed that Rutiodon's group, Phytosauria, was not closely related to other traditional "crurotarsans", at least compared to avemetatarsalians such as pterosaurs and dinosaurs. As a result, Crurotarsi could be a much broader clade than Pseudosuchia.[4] Other recent studies support a more traditional phylogeny.[5]

Contrary to popular belief, crocodilians differ significantly from their ancestors and distant relatives, as Pseudosuchia contains a staggering diversity of reptiles with many different lifestyles. Early pseudosuchians were successful in the Triassic period. They included giant, quadrupedal apex predators such as Saurosuchus, Prestosuchus, and Fasolasuchus. Ornithosuchids were large scavengers, while erpetosuchids and gracilisuchids were small, light-footed predators. A few groups acquired herbivorous diets, such as the heavily armored aetosaurs, and several were bipedal, such as Poposaurus and Postosuchus. The bizarre, ornithomimid-like shuvosaurids were both bipedal and herbivorous, with toothless beaks.[4]

Many of these Triassic pseudosuchian groups went extinct at or before the Triassic–Jurassic extinction event. However, one group, the crocodylomorphs, survived the major extinction. Crocodylomorphs themselves evolved a diverse array of lifestyles during the Jurassic and Cretaceous periods, although only a single subset of crocodylomorphs, the Crocodilia, survive to the present day. Living crocodilians include crocodiles, alligators, caimans, and gavialids.

  1. ^ Butler, Richard J.; Brusatte, Stephen L.; Reich, Mike; Nesbitt, Sterling J.; Schoch, Rainer R.; Hornung, Jahn J. (2011). "The sail-backed reptile Ctenosauriscus from the latest Early Triassic of Germany and the timing and biogeography of the early archosaur radiation". PLOS ONE. 6 (10): e25693. Bibcode:2011PLoSO...625693B. doi:10.1371/journal.pone.0025693. PMC 3194824. PMID 22022431.
  2. ^ Cite error: The named reference BC88 was invoked but never defined (see the help page).
  3. ^ Colbert, Edwin Harris; Knight, Charles Robert (1951). The Dinosaur Book: The ruling reptiles and their relatives. New York, NY: McGraw-Hill. p. 153.
  4. ^ a b Cite error: The named reference NSJ11 was invoked but never defined (see the help page).
  5. ^ Ezcurra, Martín D.; Fiorelli, Lucas E.; Martinelli, Agustín G.; Rocher, Sebastián; von Baczko, M. Belén; Ezpeleta, Miguel; Taborda, Jeremías R.A.; Hechenleitner, E. Martín; Trotteyn, M. Jimena; Desojo, Julia B. (11 September 2017). "Deep faunistic turnovers preceded the rise of dinosaurs in southwestern Pangaea". Nature Ecology & Evolution. 1 (10): 1477–1483. Bibcode:2017NatEE...1.1477E. doi:10.1038/s41559-017-0305-5. hdl:11336/41466. ISSN 2397-334X. PMID 29185518. S2CID 256707805.