What characteristic defines the group of flightless birds known as ratites, which includes the kiwi?
Answer
A flat sternum lacking the keel necessary to anchor large flight muscles
Ratites are characterized fundamentally by a structural difference in their sternum, or breastbone. Unlike flying birds, which possess a prominent ridge called a keel extending from the sternum to provide a large surface area for the powerful flight muscles to attach, ratites have a flat sternum. This anatomical feature signifies the complete loss of the ability to fly, as the necessary muscle anchorage is absent. This shared trait connects the kiwi not only to the Moa and elephant birds but also to modern large ratites like ostriches, rheas, and emus, establishing their classification within this group despite immense evolutionary distance.
Related Questions
Which extinct Madagascan bird is the kiwi's nearest living kin based on genetic mapping?What characteristic defines the group of flightless birds known as ratites, which includes the kiwi?What primary evidence led older studies to suggest the kiwi was a close cousin of the extinct Moa?Where are the external nares, which enhance the kiwi's sense of smell, uniquely situated on its bill?What does the divergence timeline suggest about the kiwi ancestors before they lost flight?The current evolutionary narrative suggests the kiwi lineage diverged from other ratites very early on. Approximately how long ago might this separation have occurred?What specific physical characteristics define the kiwi's terrestrial adaptation in New Zealand?Why has the kiwi's morphology, such as flightlessness, proven scientifically misleading about its deep ancestry?What threat do modern invasive mammalian predators like stoats exploit in the kiwi population?What hypothesis regarding kiwi ancestors was briefly supported by a fossil discovery concerning geography?