Ornithodira

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Ornithodira
Various members of the Ornithodira, clockwise from top left: Tupuxuara, Alamosaurus, Tsintaosaurus, Daspletosaurus, Pentaceratops, crane (Grus grus).

Various members of the Ornithodira, clockwise from top left: Tupuxuara , Alamosaurus , Tsintaosaurus , Daspletosaurus , Pentaceratops , crane ( Grus grus ).

Temporal occurrence
Upper Triassic to Holocene
220 to 0 million years
Locations
  • Worldwide
Systematics
Land vertebrates (Tetrapoda)
Sauropsida
Diapsida
Archosauria
Ornithodira
Scientific name
Ornithodira
Gauthier , 1986

The ornithodira are a large group of archosaurs . It is a so-called node-based taxon which is defined as the clade the last common ancestor of the Flugsaurier (Pterosauria) and dinosaurs and all its descendants (and thus also the birds comprises).

Etymology and Concept

The name Ornithodira is composed of the Greek prefix ὀρνιθο- ( ornitho- ) for terms related to birds and the word δειρή ( deire ) for "neck". It refers to a characteristic feature of this group, the S-shaped curved cervical spine, as it is still typical for birds today, and was coined by Jacques Gauthier in 1986.

features

The combination of pterosaurs, dinosaurs and a few other taxa in a common group is based on the S-shaped curved cervical spine, the typical structure of the ankle, with the joint between the "upper" (proximal) tarsus astragalus , which is closer to the knee joint and calcaneus and the "lower", closer to the tip of the foot (distal) tarsal bone (tarsalia distalia). One speaks here of a mesotarsal joint (joint in the "middle" of the tarsus). This arrangement in connection with elongated toe bones allows the animals a digitigrade locomotion, i.e. walking on their toes. The Ornithodira are compared to their sister group Crurotarsi , consisting of some extinct taxa such as the Phytosauria and the more recent crocodiles , in which the ankle lies between astragalus and calcaneus, which allows their representatives to appear with the entire sole of the foot. With the exception of a few groups of dinosaurs, the Ornithodira do not have any bone platelets embedded in the dorsal skin (so-called dorsal osteoderms), which are typical of crurotarsians and today's crocodiles.

Systematics

Since the genus Scleromochlus , which was considered the basal representative of the pterosaurs in the past, is outside of the ornithodira according to recent analyzes, the ornithodira are now not the sister taxon of the Crurotarsi, but the sister taxon of Scleromochlus .

literature