- Ornithodira
Taxobox
name = Ornithodirans
fossil_range =Middle Triassic - Recent
image_width = 250px
image_caption =
regnum =Animal ia
phylum = Chordata
classis =Sauropsid a
subclassis =Diapsida
infraclassis =Archosauromorpha
unranked_ordo =Archosauria
unranked_familia = Ornithodira
unranked_familia_authority = Gauthier, 1986
subdivision_ranks = Clades
subdivision =
*Dinosauromorpha
*Pterosauromorpha Ornithodira is a
clade within the larger groupArchosaur ia.In 1986
Jacques Gauthier coined the name for a node clade, containing the last common ancestor of thedinosaur s and thepterosaurs and all of its descendants. In 1991Paul Sereno was the first to give a formal definition, that explicitly included "Scleromochlus " and thus potentially was a larger group than Ornithodira "sensu Gauthier". In 1999 Michael Benton concluded that "Scleromochlus" was indeed outside of Ornithodira "sensu Gauthier"; that year he defined a stem cladeAvemetatarsalia for all Archosauria "sensu Gauthier" (Benton's ownAvesuchia ) that were closer to dinosaurs than toCrocodylia . 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 subclade s:Dinosauromorpha andPterosauromorpha .Dinosauromorpha contains more basal forms like "
Lagerpeton " and "Marasuchus " and as more derived forms thedinosaur s, to a subgroup of which, the theropods, according to most modern scientists thebirds belong. The Ornithodira are therefore still extant.Pterosauromorpha contains
Pterosaur ia, which are the famous flying reptiles, and as far as is known the firstvertebrate s capable of true flight. Most researchers think pterosaurians had neither an S-curved neck, nor an uprightgait : 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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