What do archosaurs include?
archosaur, (subclass Archosauria), any of various reptiles, including all crocodiles and birds and all descendants of their most recent common ancestor.
When did archosaurs exist?
The first archosauromorphs (relatives of the true archosaurs) appear in the fossil record in the Early Triassic, about 245 million years ago, just after the great end-Permian extinction.
What two groups did archosaurs split into?
About 250 million years ago, the archosaurs split into two groups: a bird-like group that evolved into dinosaurs, birds, and pterosaurs, and a crocodile-like group that includes the alligators and crocs alive today and a diversity of now-extinct relatives.
Do archosaurs produce milk?
Dinosaurs did not have mammary glands, much less breasts – that’s only a feature of some placental mammals, such as primates, elephants, and sea cows – so I’m not entirely sure why Dinah had to be covered up. The top implies the existence of something that could not have existed.
What is the difference between Saurischians and ornithischians?
In saurischian dinosaurs, this bone points toward the front of the animal, and flares into a keel at the forward end. Ornithischians have a reversed pubis, which points toward the tail and lies alongside and parallel to the ischium. Additionally, some ornithischians have a projection at the forward end of the pubis.
What is the difference between archosaurs and lepidosaurs?
The anatomy and functional morphology of archosaur and lepidosaur jaws differ in several ways. For example, archosaur teeth are implanted within sockets in the jaw, while lepidosaur teeth are implanted either to the sides or apices of the jaw49,50.
What is reverse pubis?
Ornithischians have a reversed pubis, which points toward the tail and lies alongside and parallel to the ischium. Additionally, some ornithischians have a projection at the forward end of the pubis. The first recognition of the two groups was made by H.G. Seeley in 1888.
What is a dinosaur pubis?
The dinosaur hip is primarily divided into three parts. There is the ilium (the large, upper flange of the hips), the ischium (a smaller spine that runs below and behind) and the pubis (another slender extension of the lower hip that can be found in various orientations from front to back).
Which group has the crocodile reversed ankle?
This condition is often referred to as a “crocodile-normal” ankle, as it is the most common ankle type in crurotarsans. Ornithosuchids are unique among crurotarsans, and all other archosaurs, in their possession of a “crocodile-reversed” ankle.
Do humans have synapsid skull?
Humans are synapsids, as well. Most mammals are viviparous and give birth to live young rather than laying eggs with the exception being the monotremes.
What is the difference between sauropsids and synapsids?
Synapsids include all mammals, including extinct mammalian species. Synapsids also include therapsids, which were mammal-like reptiles from which mammals evolved. Sauropsids include reptiles and birds and can be further divided into anapsids and diapsids.
What are the extinct archosaurs?
Extinct archosaurs include non-avian dinosaurs, pterosaurs, and extinct relatives of crocodilians. Modern paleontologists define Archosauria as a crown group that includes the most recent common ancestor of living birds and crocodilians, and all of its descendants.
Is Archosauria a type of archosaur?
Archosauria is within the larger clade Archosauriformes, which includes some close relatives of archosaurs, such as proterochampsids and euparkeriids. These relatives are often referred to as archosaurs despite being placed outside of the crown group Archosauria in a more basal position within Archosauriformes.
What are the advantages of archosaur lungs?
The better efficiency in gas transfer seen in archosaur lungs may have been advantageous during the times of low atmospheric oxygen which are thought to have existed during the Mesozoic. Most (if not all) archosaurs are oviparous. Birds and crocodilians lay hard-shelled eggs, as did extinct dinosaurs, and crocodylomorphs.
Why are there no viviparous archosaurs?
The pelvic anatomy of Cricosaurus and other metriorhynchids and fossilized embryos belonging to the non-archosaur archosauromorph Dinocephalosaurus, together suggest that the lack of viviparity among archosaurs may be a consequence of lineage-specific restrictions.