Editing Carinatae

{{Short description|Group of birds}}
{{about|bird taxonomy|the pottery shape|Carinate}}
[[File:Bréchet.png|thumb|Bréchet, keel sternum]]

'''Carinatae''' is the group of all [[bird]]s and their extinct relatives to possess a [[Keel (bird anatomy)|keel]], or "carina", on the underside of the [[breastbone]] used to anchor large flight muscles.

==Definition==
Traditionally, Carinatae were defined as all birds whose [[sternum]] (breast bone) has a [[keel (bird)|keel]] (''carina''). The keel is a strong median ridge running down the length of the sternum. This is an important area for the attachment of flight muscles. Thus, all flying birds have a pronounced keel. [[Ratite]]s, all of which are flightless, lack a strong keel. Thus, living birds were divided into carinatae (keeled) and ratites (from ''ratis'', "raft", referring to the flatness of the sternum). The difficulty with this scheme [[phylogenetics|phylogenetically]] was that some flightless birds, without strong keels, are descended directly from ordinary flying birds possessing one. Examples include the [[kākāpō]], a flightless [[parrot]], and the [[dodo]], a columbiform (the [[pigeon]] family). Neither of these birds are a ratite. Thus, this supposedly distinctive feature was easy to use, but had nothing to do with actual phylogenetic relationship.{{cn|date=October 2020}}

Beginning in the 1980s, Carinatae was given several [[phylogenetic]] definitions. The first was as a node-based [[clade]] uniting ''[[Ichthyornis]]'' with modern birds.<ref name = "Cracraft"/> However, in many analyses, this definition would be synonymous with the more widely used name [[Ornithurae]]. An alternate definition was provided in 2001, naming Carinatae an [[apomorphy]]-based clade defined by the presence of a keeled sternum.<ref name="Gauthier"/>

The most primitive known bird relative with a keeled breastbone is ''[[Confuciusornis]]''. While some specimens of this stem-bird have flat breastbones, some show a small ridge that could have supported a cartilaginous keel.<ref name = "Chiappe"/>

==References==
{{reflist |refs = 
<ref name = "Chiappe">{{cite journal |last1=Chiappe |first1=Luis M. |last2=Ji |first2=Shu' An |last3=Ji |first3=Qiang |last4=Norell |first4=Mark A. |year=1999 |title=Anatomy and systematics of the Confuciusornithidae (Theropoda, Aves) from the late Mesozoic of northeastern China |journal=Bulletin of the AMNH |volume=242 |url=https://www.researchgate.net/publication/270509827}}</ref>

<ref name = "Cracraft">{{cite journal |last=Cracraft |first=Joel |year=1986 |title=The origin and early diversification of birds |journal=[[Paleobiology (journal)|Paleobiology]] |volume=12 |issue=4 |pages=383–399 |doi=10.1017/s0094837300003122|bibcode=1986Pbio...12..383C |s2cid=89557960 }}</ref>

<ref name="Gauthier">{{cite conference |last1=Gauthier |first1=Jacques |last2=de Queiroz |first2=Kevin |year=2001 |title=Feathered dinosaurs, flying dinosaurs, crown dinosaurs, and the name "Aves" |conference=New Perspectives on the Origin and Early Evolution of Birds: Proceedings of the International Symposium in Honor of John H. Ostrum |pages=7–41 |publisher = Peabody Museum of Natural History, Yale University |url=https://www.researchgate.net/publication/40662575}}</ref>
}}

[[Category:Euornithes]]