May 28 2010

Anatomy: Tarsus

Published by at 7:13 am under Bird Anatomy

I’m back on track after a side trip to pin-feathers.

Today’s anatomy lesson goes back to the birds’ feet.  Last time I talked about toes.

What’s connected to the toes?   The foot.

So where’s the bird’s foot?

It’s called the tarsus, but we call it the bird’s leg.  Weird, eh?

Human toes are connected to our feet and our feet walk on the ground. To make this possible, we have many bones in our feet and ankles.

Birds walk on their toes and have one bone, the tarsometatarsus, that’s formed by the fusion of what would have been their ankle (tarsal) and foot (metatarsal) bones if they were mammals.

So how is this different from mammals?  Cats and dogs walk on their toes too but their foot bones are not fused.  What they have in common with birds is that all of these animals look as if their knees bend backwards because their “knees” are actually their ankles.

Confusing?  Well, fortunately you can still call this body part a “leg” in general conversation.  When you want to be exact you can call it a tarsus (indicated by the red arrow).

(photo of a palm warbler by Chuck Tague)

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