What is the meaning of Archosauria?

What is an archosaur group?

Archosauria is normally defined as a crown group, which means that it only includes descendants of the last common ancestors of its living representatives. In the case of archosaurs, these are birds and crocodilians.

Are archosaurs diapsids?

Archosauria ( lit. ‘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.

Were archosaurs better at conserving water than synapsids?

Archosaurs were probably better at conserving water than early synapsids because: Modern diapsids (lizards, snakes, crocodilians, birds) excrete uric acid, which can be excreted as a paste, resulting in low water loss as opposed to a more dilute urine.

What is Archosauria and what are its characteristics?

Archosauria is defined as the most recent common ancestor of Crocodylia and Aves, and all of that ancestor’s descendants. Archosaurs are diagnosed by a number of anatomical features and also by behavioral characteristics such as nest building and parental care of young.

What group does the archosaur belong to?

This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most recent common ancestor of living birds and crocodilians.

What is a diapsid lizard?

Diapsids (” two arches “) are a subclass of reptiles that developed two holes (temporal fenestra) in each side of their skulls, approximately 300 million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and include all crocodiles, lizards, snakes, worm lizards, tuatara and birds.

Is a snake a diapsid?

Modern diapsids include lizards, snakes, turtles, birds, and crocodylians; extinct diapsids include dinosaurs, pterosaurs, ichthyosaurs, and many other familiar taxa. The stem-based name Diapsida is derived from the presence of a pair of fenestrae in the temporal region of the skull.

How many diapsid reptiles are there?

There are at least 7,925 species of diapsid reptile existing in environments around the world today (over 14,600 when birds are included). Community content is available under CC-BY-SA unless otherwise noted.

What is the only living archosaur group?

Unsourced material may be challenged and removed. Birds and crocodilians (in this case a yellow-billed stork and a Nile crocodile) are the only known living archosaur groups. † Incertovenator?

Why were archosaurs better at conserving water than early synapsids?

Archosaurs were probably better at conserving water than early synapsids because: Modern diapsids (lizards, snakes, crocodilians, birds) excrete uric acid, which can be excreted as a paste, resulting in low water loss as opposed to a more dilute urine.

How did dinosaurs manage to conserve water?

Modern diapsids (lizards, snakes, crocodilians, birds) excrete uric acid, which can be excreted as a paste, resulting in low water loss as opposed to a more dilute urine. It is reasonable to suppose that archosaurs (the ancestors of crocodilians, dinosaurs and pterosaurs) also excreted uric acid, and therefore were good at conserving water.

What happened to the synapsids after the extinction of the dinosaurs?

Very few large synapsids survived the event, and one form, Lystrosaurus (a herbivorous dicynodont ), attained a widespread distribution soon after the extinction. Instead, archosaurs and other archosauriforms quickly became the dominant land vertebrates in the early Triassic.

Where did archosaurs come from?

The ancestral archosaurs probably originated some 250 million years or so ago, in the late Permian Period. Their descendants (such as the dinosaurs) dominated the realm of the terrestrial vertebrates for a majority of the Mesozoic Era. Today, only the birds and crocodilians exist to provide a glimpse into the past glory of archosaurs.

What are the characteristics of an archosaur?

Other typical archosaurian characteristics include another opening in the lower jaw (the mandibular fenestra), a high narrow skull with a pointed snout, teeth set in sockets (called thecodont tooth implantation), and a modified ankle joint. The ancestral archosaurs probably originated some 250 million years or so ago, in the late Permian Period.

How many diapsids are there in the world?

Although some diapsids have lost either one hole (lizards), or both holes (snakes and turtles), or have a heavily restructured skull (modern birds), they are still classified as diapsids based on their ancestry. At least 17,084 species of diapsid animals are extant: 9,159 birds, and 7,925 snakes, lizards, tuatara, turtles, and crocodiles.

Why did archosaurs become the dominant vertebrates in the Triassic period?

But archosaurs quickly became the dominant land vertebrates in the early Triassic. The two most commonly suggested explanations for this are: Archosaurs made more rapid progress towards erect limbs than synapsids, and this gave them greater stamina by avoiding Carrier’s constraint.

What are the synapomorphies of archosaurs?

The simplest and most widely-agreed synapomorphies of archosaurs are: Teeth set in sockets, which makes them less likely to be torn loose during feeding. This feature is responsible for the name ” thecodonts ” (“socket teeth”), which paleontologists used to apply to all or most archosaurs.

Were dinosaurs good at conserving water?

It is reasonable to suppose that archosaurs (diapsids and ancestors of crocodilians, dinosaurs and birds) also excreted uric acid, and therefore were good at conserving water. The aglandular (glandless) skins of diapsids would also have helped to conserve water.

What was the first dinosaur to live in water?

The discovery of the remains of the first aquatic dinosaur, Spinosaurus aegyptiacus, in Morocco has been described as ‘game-changing’. The newly-discovered tail fossil of the first “river monster” dinosaur shows the giant predator was a powerful swimmer and the first known to have lived in the water.

Why should we be surprised by the existence of dinosaurs?

Why should this be surprising? Well, the fact is that dinosaurs, pterosaurs, and crocodiles are all descended from archosaurs, the “ruling lizards” of the late Permian and early Triassic periods.

How do paleontologists use dinosaurs to study evolution?

Dozens of features distinguish dinosaurs from other reptiles, such as bones of the lower arm being longer than the upper arm. And when paleontologists combine and compare such characteristics between various reptiles, they can create a tree of evolutionary history that reveals the relationships between different groups.