Archosauria (crocodiles, dinosaurs, birds and their relatives)

Life > Eukaryotes > Opisthokonta > Metazoa (animals) > Bilateria > Deuterostomia > Chordata > Craniata > Vertebrata (vertebrates)  > Gnathostomata (jawed vertebrates) > Teleostomi (teleost fish) > Osteichthyes (bony fish) > Class: Sarcopterygii (lobe-finned fish) > Stegocephalia (terrestrial vertebrates) > Tetrapoda (four-legged vertebrates) > Reptiliomorpha > Amniota > Reptilia >  Romeriida > Diapsida > Archosauromorpha > Archosauriformes

The oldest archosaur fossils date back to the Early Triassic (245 million years ago) and show the following skeletal modifications that distinguish them from their archosauromorph ancestors:

  • no pineal foramen (opening) in the roof of the skull;

  • no teeth on the palate

  • no bony plates (intercentra) between the vertebrae;

  • special flexible ankle joint;

  • bony armour in the skin covering the body; and

  • a third opening in the skull, between the eye socket and the nasal cavity the antorbital fenestra.


Based on Nesbitt (2011). '#' indicates the taxon is known only from fossils, with no living representatives. 

Pseudosuchia (crocodiles and extinct relatives)

In the phylogeny of Brusatte et al. (2010), the sister group to the Avemetatarsalia is given as Crurotarsi, not Pseudosuchia. The position of Crurotarsi is defined on the joint presence of both crocodiles and phytosaurs and as Nesbitt (2011) places phytosaurs as the sister group to the archosaurs, Crurotarsi ends up at a higher level than the archosaurs (see Archosauriformes).


# Ornithosuchidae




# basal suchians

Include the following fossil taxa, none of which is known from fossils collected in southern Africa: Gracilisuchus (from Argentina), Turfanosuchus (from China), Aetosauria (from Europe and the USA and including Revueltosaurus, Aetosaurus, Stagonolepis and Longosuchus) and Ticinosuchus (from Switzerland).




# Poposauroidea

Includes the following fossil genera, none of which is known from fossils collected in southern Africa: Qianosuchus (from China), Arizonasaurus (from USA), Xilousuchus (from China), Poposaurus (from USA), Lotosaurus (from China), Sillosuchus (from Argentina), Shuvosaurus (from USA) and Effigia (from USA).




# basal loricatans

Includes the following fossil groups, none of which is known from fossils collected in southern Africa: Prestosuchus (from Brazil), Saurosuchus (from Argentina), Batrachotomus (from Germany), Fasolasuchus (from Argentina) and the Rauisuchidae (from Brazil, Poland and the USA and including Rauisuchus, Polonosuchus and Postasuchus).


Crocodylomorpha (crocodiles and extinct relatives)


Avemetatarsalia (dinosaurs, birds and extinct relatives)


# Pterosauromorpha




# Lagerpetidae




# basal Dinosauriformes


# Silesauridae


Dinosauria (dinosaurs, including birds)



  • Nesbitt SJ. 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 1-292.

Text by Roger Smith and Hamish Robertson

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