Archosaurs

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Subclass: Diapsida
Infraclass: Archosauromorpha
Unranked: Archosauria (Cope, 1869)
Groups: Crurotarsi (Aetosauria, Crocodilia (crocodiles), Phytosauria, Rauisuchia), Ornithodira (Pterosauria, Marasuchus, Dinosauria (Aves (birds)))

Archosaurs (Greek for ‘ruling lizards’) are a group of diapsid reptiles that initially evolved from Archosauriform ancestors during the Olenekian (Decrease Triassic Period). They’re represented currently by birds and crocodiles. Archosaurs are set apart by possessing socketed teeth (a feature that inspired the standard name, ‘thecodonts’, for the Triassic forms) and four-chambered hearts, among other qualities. Most early types have been carnivores, with narrow serrated meat-tearing teeth. Their “reptilian” metabolism look to have offered them a clear benefit over the mammal-like therapsids that have been their contemporaries in the arid interiors and powerful monsoon climates that had been the all-natural result on the single world-continent, Pangaea. Thus, whereas the Permian was dominated by synapsids, the Triassic came to become dominated by sauropsids.

You will discover two primary groups of archosaurs – the Ornithodira which have been insignificant for the duration of the Middle Triassic but within the Late Triassic radiated because the dinosaurs and pterosaurs; and the Crurotarsi, which have been the predominant group at this time, and included many purely Triassic groups like the rauisuchians, the phytosaurs, as well as the herbivorous aetosaurs, too as the ancestors from the crocodilians.

Quite a few these archosaur groups – chiefly those substantial Crurotarsi which can be in pre-cladistic books referred to as the Thecodonts – became extinct 195 million years ago, through the Triassic-Jurassic extinction occasion. The survivors – the Dinosaurs and also the Pterosaurs among the Ornithodira, and 1st the Sphenosuchia and Protosuchia then their descendants the Crocodilia amongst the Crurotarsi – flourished through the Jurassic and Cretaceous Periods. The dinosaurs dominated the land, the pterosaurs and later an additional archosaurian group, the birds, dominated the air,as well as the crocodiles dominated the rivers and swamps and also invaded the seas (the Teleosaurs and Metriorhynchidae).

The majority of these taxa perished 65 million years ago, during the Cretaceous-Tertiary extinction occasion. The only groups of archosaurs to continue by way of for the Tertiary and, ultimately, towards the present day, are the birds (which are descended in the dinosaurs) plus the crocodylia (which involve all modern crocodiles, alligators, and gharials).

Birds are traditionally treated as a separate class, Aves, although the rest of your archosaurs are treated as a subclass or infraclass, Archosauria, inside the class Reptilia. More not too long ago, with the cladistic process dominating Biology, only monophyletic groups are regarded as valid and birds are included within the division Archosauria.

Taxonomy

• Infraclass Archosauromorpha
  • (unranked) Archosauriformes
    • (unranked) ARCHOSAURIA
      • (unranked) Crurotarsi (“Pseudosuchia”)
        • Order Phytosauria
        • Order Aetosauria
        • Order Rauisuchia
          • Order Crocodilia
      • (unranked) Ornithodira (“Ornithosuchia” sensu Gauthier but without Ornithosuchidae)
        • Order Pterosauria
        • Superorder Dinosauria
          • Class Aves

References

• Benton, M. J. (2004), Vertebrate Paleontology, 3rd ed. Blackwell Science Ltd
• Carroll, R. L. (1988), Vertebrate Paleontology and Evolution, W. H. Freeman and Co. New York

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