| Ornithodirans Fossil range: Middle Triassic - Recent |
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Ornithodira is a clade within the larger group Archosauria. The Middle Triassic (also known as Muschelkalk) is the second of three epochs of the Triassic period. Chordates ( Phylum Chordata) are a group of Animals that includes the Vertebrates together with several closely related Invertebrates Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Diapsids ("two arches" are a group of Reptiles that developed two holes ( Temporal fenestra) in each side of their Skulls about 300 Million Archosauromorpha ( Greek for "ruling lizard forms" is an Infraclass of Diapsid Reptiles that first appeared during the late Permian Archosaurs ( Greek for 'ruling lizards' are a group of Diapsid Reptiles represented by Modern birds and Crocodilians This group also Jacques Armand Gauthier is a vertebrate paleontologist, comparative morphologist, and systematist and one of the founders of the use of Cladistics in biology Dinosauromorpha is the name of a Clade of Archosaurs that includes the direct sister groups of Dinosaurs and the order Dinosauria itself For other meanings see Pterodactyl (disambiguation. Pterosaurs (ˈtɛrəsɔr from the Greek πτερόσαυρος pterosauros A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor Archosaurs ( Greek for 'ruling lizards' are a group of Diapsid Reptiles represented by Modern birds and Crocodilians This group also
In 1986 Jacques Gauthier coined the name for a node clade, containing the last common ancestor of the dinosaurs and the pterosaurs and all of its descendants. Jacques Armand Gauthier is a vertebrate paleontologist, comparative morphologist, and systematist and one of the founders of the use of Cladistics in biology For other meanings see Pterodactyl (disambiguation. Pterosaurs (ˈtɛrəsɔr from the Greek πτερόσαυρος pterosauros In 1991 Paul Sereno was the first to give a formal definition, that explicitly included Scleromochlus and thus potentially was a larger group than Ornithodira sensu Gauthier. Paul Callistus Sereno (born October 11 1957) is an American paleontologist who is the discoverer of several new Dinosaur species on Scleromochlus is an Extinct Genus of small Ornithodiran from the Late Triassic period In 1999 Michael Benton concluded that Scleromochlus was indeed outside of Ornithodira sensu Gauthier; that year he defined a stem clade Avemetatarsalia for all Archosauria sensu Gauthier (Benton's own Avesuchia) that were closer to dinosaurs than to Crocodylia. Michael Benton may refer to Michael J Benton, professor of vertebrate palaeontology at the University of Bristol Michael L Avemetatarsalia (meaning "bird Metatarsals " is a Clade name established by British palaeontologist Michael Benton in 1999 for all Avesuchians Crocodilia is an order of large Reptiles that appeared about 84 million years ago in the late Cretaceous Period ( Campanian stage In 2004 Benton gave a formal definition of Ornithodira sensu Gauthier. In 2005 Sereno stated the opinion that Ornithodira was not a useful concept, whereas Avemetatarsalia was.
Members of Ornithodira are characterized by an upright gait and an S-curved neck, hence the name "Ornithodira" ("bird necks"). It is by definition strictly divided into two subclades: Dinosauromorpha and Pterosauromorpha. A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor Dinosauromorpha is the name of a Clade of Archosaurs that includes the direct sister groups of Dinosaurs and the order Dinosauria itself For other meanings see Pterodactyl (disambiguation. Pterosaurs (ˈtɛrəsɔr from the Greek πτερόσαυρος pterosauros
Dinosauromorpha contains more basal forms like Lagerpeton and Marasuchus and as more derived forms the dinosaurs, to a subgroup of which, the theropods, according to most modern scientists the birds belong. Lagerpeton is the name given to a genus of basal dinosauromorph from the Ladinian (Middle Triassic) Marasuchus is a genus of Dinosaur -like Ornithodiran from the middle Triassic Period of Argentina. Theropods (ˈθɪərəpɒd theropoda /θiːˈrɒpədə/ 'beast feet' are a group of Bipedal Saurischian Dinosaurs Although they were primarily Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. The Ornithodira are therefore still extant.
Pterosauromorpha contains Pterosauria, which are the famous flying reptiles, and as far as is known the first vertebrates capable of true flight. For other meanings see Pterodactyl (disambiguation. Pterosaurs (ˈtɛrəsɔr from the Greek πτερόσαυρος pterosauros Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes Flight is the process by which an object achieves sustained movement either through the Air (or movement beyond Earth's atmosphere, in the case of Most researchers think pterosaurians had neither an S-curved neck, nor an upright gait: the clade Ornithodira is defined on basis of ancestry, not characters — and it is always possible later descendants show a change in characters.
Phylogeny
Cladogram after Ezcurra (2006):
Ornithodira |--Pterosauromorpha | | | `--Pterosauria `--Dinosauromorpha |--Lagerpeton `--Dinosauriformes |--Marasuchus `--+--Pseudolagosuchus `--+--Silesaurus `--+--Eucoelophysis `--Dinosauria |--Saurischia | |--Herrerasauridae | `--Eusaurischia | |--Theropoda | `--Sauropodomorpha `--Ornithischia
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