The first known archosaurs appeared in the Middle Triassic Period (about 246 million to 229 million years ago). They evolved from an earlier group of diapsid reptiles, diapsids having two openings in the skull behind the eye.
Are crocodiles archosaurs?
Crocodilians and birds are the two extant clades of archosaurs, a group that includes the extinct dinosaurs and pterosaurs. Fossils suggest that living crocodilians (alligators, crocodiles, and gharials) have a most recent common ancestor 80 to 100 million years ago.
What is the particular evolutionary importance of archosaurs?
Archosaurs appeared in fossil record sometime in the Triassic and are thought to have evolved ears sensitive to airborne sound sometime later. The evolution of tympanic ear would have increased both the sensitivity and the high-frequency response of the ears to airborne sound.
When did archosaurs become extinct?
about 200 million years ago
Extinction and survival Crocodylomorphs, pterosaurs and dinosaurs survived the Triassic–Jurassic extinction event about 200 million years ago, but other archosaurs had become extinct at or prior to the Triassic-Jurassic boundary.
How do archosaurs breathe?
Ventilation is achieved through a system of air sacs, which expand and contract (driven by motion of the ribs and the sternum, or breastbone) to create air flow through the lungs. The question is whether dinosaurs also had such a lung–air sac system, and whether they had the same high capacity for gas exchange.
Is Ostrich an Archosaur?
Living archosaurs comprise birds (dinosaurs), and their sister group, the crocodilians. Archosaurs appeared in fossil record sometime in the Triassic and are thought to have evolved ears sensitive to airborne sound sometime later. Palaeognaths are generally flightless and include such birds as the ostrich.
How did dinosaurs start existing?
Dinosaurs were a successful group of animals that emerged between 240 million and 230 million years ago and came to rule the world until about 66 million years ago, when a giant asteroid slammed into Earth.
In what epoch did dinosaurs go extinct?
Cretaceous Period
Dinosaurs went extinct about 65 million years ago (at the end of the Cretaceous Period), after living on Earth for about 165 million years.
What are the characteristics of early archosaur evolution?
Early archosaur evolution is characterized by high rates of homoplasy, long ghost lineages, and high rates of character evolution. These data imply that much of the early history of Archosauria has not been recovered from the fossil record.
How old are archosaurs?
Archosaurs have a nearly 250 million year record that originated shortly after the Permian-Triassic extinction event and is continued today by two extant clades, the crocodylians and the avians.
What is the only living group of archosaurs?
Birds and crocodilians (in this case a yellow-billed stork and a Nile crocodile) are the only known living archosaur groups. Archosauria (“ruling reptiles”) is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of term which includes birds.
What is the classification of Archosauria?
Archosaurs are a group of diapsid amniotes whose living representatives consist of birds and crocodilians. This group also includes all extinct dinosaurs, extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most recent common ancestor…
