28 May 2010

Today’s anatomy lesson is about legs.

It’s easy to identify the birds’ toes, but where are their ankles and what’s in between?

Like cats and dogs, birds walk on their toes and look as if their knees bend backwards. Their “knees” are actually their ankles.

Between toes and ankles birds have a single bone, the tarsometatarsus, that’s the fusion of what would have been ankle (tarsal) and foot (metatarsal) bones if they were mammals.

This body part is called the tarsus. Plural is tarsi.

Fortunately we can still call it a “leg” in general conversation. 

(photo of a palm warbler by Chuck Tague, annotated by Kate St. John)