Ornithodira

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

• Worldwide

The Ornithodira are a large group of archosaurs. It is a so-called node-based taxon, which is defined as the clade 's common ancestor pterosaur ( pterodactyl ) and dinosaurs and all his descendants includes ( and therefore the birds).

Etymology and concept

The name Ornithodira is Composed of the Greek prefix ὀρνιθο ( ornithological ) 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 spine, as is typical for birds today and was coined by Jacques Gauthier in 1986.

Features

The summary of the pterosaurs, dinosaurs and some other taxa to a common group is based, in addition to the S- shaped curved spine, to the typical construction of the ankle where the joint between the "upper", located closer to the knee joint ( proximal ) tarsal bones Astragalus and calcaneus and the "lower", closer to the toe (distal) tarsal bones ( tarsals distalia ) runs. We speak here of a Mesotarsalgelenk ( Gelenkung in the "middle " of the tarsus ). This arrangement, in conjunction with extended toe bones allowed the animals a digitigrade locomotion, ie the transition on their toes. The Ornithodira be their sister group Crurotarsi consisting of some extinct taxa such as the Phytosauria well as from recent crocodiles, faced, in which the ankle joint between astragalus and calcaneus is what can occur with the entire sole of their representatives. The Ornithodira own, except for a few groups of dinosaurs, not embedded in the dorsal skin of the bone plate ( so-called dorsal osteoderms ), as they are for typical Crurotarsier and today's crocodiles.

System

Since the genus Scleromochlus, which was considered representative of the basal pterosaurs in the past, recent analyzes indicate stands outside the Ornithodira, the Ornithodira now not the sister taxon of Crurotarsi but the sister taxon of Scleromochlus.

• Archosauria ( archosaurs crown group Avesuchia ) Crurotarsi
• Avemetatarsalia Scleromochlus †
• Ornithodira Pterosaur ( Pterosauria ) †
• Dinosauromorpha Lagerpeton †
• Dinosauriformes Marasuchus †
• Asilisaurus †
• Dinosaurs ( Dinosauria ) Birds ( Aves, Avialae )