Are there any birds whose legs fold the same way human legs do, in a knee, instead of an elbow which is what all the birds I know have?
$\begingroup$
$\endgroup$
$\begingroup$
$\endgroup$
The joint you are thinking of is not a knee, nor is it an elbow, instead it is an ankle which is bending the same way as us humans. You can see from the below diagram that the knee - the joint between the femur and tibia - is just further up the leg normally hidden by feathers.
Birds have a comparatively elongated metatarsus which gives the impression that the knee bends backwards more like an elbow, but it's just the ankle. (Image from here)
I also liked this diagram from a blogpost on a similar theme...
To follow up there appears to be no animals whose ankles bend the "wrong" way.
http://www.answers.com/Q/Which_animal_has_backward_knees
http://www.ehow.com/info_12317202_birds-knees-backwards.html#page=1
Though these are far from conclusive resources. I'd guess the way knee is defined (it means something to humans but not to nature (a bit like the species being a concept which has weak biological bounds)) has something to do with that
-
$\begingroup$ Good point, thank you! It didn't occur to me. However, the joint I'm talking about is between Tibia and Metatarsus (ankle, right)? Are there any birds whose ankles bend backwards? $\endgroup$ – Violet Giraffe Oct 21 '14 at 16:12
-
$\begingroup$ according to the blogpost mentioned above no, no tetrapods do this $\endgroup$ – rg255 Oct 21 '14 at 16:14
-
-
$\begingroup$ +1 Nice answer. You should add a reference to the first figure thought. $\endgroup$ – fileunderwater Oct 22 '14 at 10:51
-
$\begingroup$ Did you replace the first illustration? You shouldn't have, the other one was much larger and clearer; I can hardly read anything on this one. $\endgroup$ – Violet Giraffe Oct 22 '14 at 15:06
