The projection of bone from the sternum (breastbone) of a bird or bat, to which the powerful flight muscles are attached. The sterna of flightless birds (e.g. ostrich and emu) lack keels.
Geology and Earth Sciences
1. An external, longitudinal ridge situated on the venter of an ammonoid (Ammonoidea).
2. In flying birds, a ridge projecting forward from the sternum and serving for the attachment of the enlarged pectoral muscles.