Keel (bird anatomy)
In bird anatomy, the keel or carina (pl.: carinae) is an extension of the sternum (breastbone) which runs axially along the midline of the sternum and extends outward, perpendicular to the plane of the ribs.[1] The keel provides an anchor to which the supracoracoideus (the muscle responsible for the upstroke) and pectoralis (the muscle responsible for the downstroke) attach, thereby providing adequate leverage for flight.[2] Not all birds have keels; in particular, some flightless birds lack a keel structure. Some flightless birds have a keel, such as the penguin; this is because penguins still require strong wing muscles to power underwater movement.[3]
Historically, the presence or absence of a pronounced keel structure was used as a broad classification of birds into two orders: Carinatae (from carina, "keel"), having a pronounced keel; and ratites (from ratis, "raft" – referring to the flatness of the sternum), having a subtle keel structure or lacking one entirely.[4] However, this classification has become disused as evolutionary studies have shown that many flightless birds have evolved from flighted birds.[citation needed]
See also
[edit]References
[edit]- ↑ Ramel, Gordon. "Bird Anatomy: Complete Guide – Including Feet, Skeleton & Wings". earthlife.net. Retrieved 17 March 2026.
- ↑ Pollard-Wright, Holly. "Basics of Musculoskeletal Anatomy in Birds". Veterinary Kinetics Rehab. Retrieved 17 March 2026.
- ↑ Ramel, Gordon. "Bird Anatomy: Complete Guide – Including Feet, Skeleton & Wings". earthlife.net. Retrieved 17 March 2026.
- ↑ Cummins, Jim (1 April 1996). "Anatomy of Flight". Archived from the original on 11 February 2005. Retrieved 17 March 2026.
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