Dear Wordwind: I found the site with a picture of possum with "opposable thumb"
on its hind foot where it would be useful only for climbing.
And if you look at the picture, you will see that while it is called opposable,
it does not meet primate definition, of being able to touch pad of each of
the digits. The opossum cannot touch "thumb" to the pinky. Yah, Yah, Yah.
Grumble,grumble - thumb on foot, forsooth!