''Archosaurus'' (meaning "ruling lizard") is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of carnivorous proterosuchid archosauriform

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

. Its fossils are dated to the latest Permian of

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

and

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...

, it is one of the earliest known archosauriforms. The type and only species is ''Archosaurus rossicus'', known from several fragmentary specimens which cumulatively represent parts of the skull and cervical vertebrae.Paleont. Zh. 1960 (4) It would have been long when fully grown. When first described in 1960, ''Archosaurus'' was considered the oldest known

archosaur Archosauria () or archosaurs () is a clade of diapsid sauropsid tetrapods, with birds and crocodilians being the only extant taxon, extant representatives. Although broadly classified as reptiles, which traditionally exclude birds, the cladistics ...

and a close relative of '' Proterosuchus'' from the

Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between 251.9 Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which ...

.Tatarinov, L. P. (1960). ''Otkrytie pseudozhukhii v verkhnei permi SSSR: Paleontologischeskii Zhurnal'', 1960, n. 4, p. 74-80. However, Archosauria in modern terms is considered a more restricted group which ''Archosaurus'' lies outside of. The "classic" definition of archosaur utilized prior to the widespread use of

cladistics Cladistics ( ; from Ancient Greek 'branch') is an approach to Taxonomy (biology), biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesiz ...

is now roughly equivalent to the clade Archosauriformes.Gauthier J. A. (1994): ''The diversification of the amniotes''. In: D. R. Prothero and R. M. Schoch (ed.) Major Features of Vertebrate Evolution: 129-159. Knoxville, Tennessee: The Paleontological Society. ''Archosaurus'' is still considered the oldest undisputed archosauriform, as well as one of the few valid members of the family Proterosuchidae. A 2023 study placed ''Archosaurus'' in the new subfamily Chasmatosuchinae within the proterosuchids. This would make ''Archosaurus'' significantly derived despite being the oldest known archosauriform, indicating that significant diversification already occurred among proterosuchids during the Permian.

Gallery

File:Archosaurus rossicus.png, PIN 1100/55, the holotype left premaxilla File:Archosaurus_ross1DB.jpg, Restoration File:Archosaurus Scale.svg, Size comparison

References

Proterosuchidae Prehistoric reptile genera Lopingian reptiles of Europe Fossils of Poland Permian Russia Fossil taxa described in 1960 {{Permian-reptile-stub

Gallery

See also

References