I understand that one of the things that set us primates apart from other fauna is our opposable thumbs.
Now, I've been watching squirrels eat nuts. Sometimes these nuts are so huge the squirrels have to whack away at the shell for a while before they can get to the good stuff. They hold these nuts in their hands and it looks to me like their 'thumbs' are doing much of the rotating work. In other words, they look opposable.
Dr Bill (or anyone else), can you supply any info on this?
There's a lot to be said about thumbless squirrels on the web. One site was a personal reflection of a squirrel owner who stated their family squirrel has opposable thumbs. Must sites I scanned stated that squirrels don't have opposable thumbs, but do exercise flexibility with their fingers.
I learned that opposums do have opposable thumb.
One site had a declaration that--get ready!--elephants have opposable thumbs. The things you read on the Web!
I'd say the jury's out on this one, with most witnesses stating that squirrels don't have opposable thumbs. I don't have any idea where that elephant comment came from!
WW
P.S. Oh, one definition of the opposable thumb was that it could be identified by the owner's ability to move it across the palm. Never saw an elephant do that!
Dear AS: I have seen squirrels grasp nuts, showing use of thumb. My daughter had
a pet coon that would gently take hold of dog's eyelid, and peek into eye. Dog knew
better than to move, fortunately. I have seen racoons grasping crayfish when eating
them. And dabbling food in water prior to eating.
But an anthropology site requires more than this to qualify for "opposable thumb":
"opposable thumb: an anatomical arrangement in which the fleshy tip of
the thumb can touch the fleshy tip of all the fingers."
I very much doubt that squirrels or coons can touch pad of thumb to tip of pinky.
In reply to:
I very much doubt that squirrels or coons can touch pad of thumb to tip of pinky.
...but apparently opposum's can. 
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!
Ho do you know that opposum can't touch his toe thumb to his toe pinky?
In fact, there's a lot we don't know about animals until somebody finally observes a behavior and records it.
On that one site, a lady did declare that her squirrel had little opposable thumbs. Who's to say it didn't have 'em?
On the Disney site it was suggested that we tape our thumbs to the inside of our hands, and then try to crack a nut as a squirrel does. Well, that doesn't seem fair at all. Don't the little squirrels have five fingers, even if they don't have an opposable thumb [which is still arguable since we don't know what they do with their little could-be thumbs in the middle of the night...they may spend part of their nights touching their little four fingers with their possibly opposable thumb and laughin' at us for thinkin' they cain't do it!]
Why, I just learned that a bluejay saw an injured bird, led a human being to it, and then helped feed the bird [not a jay] while the human being took care of it. And that's a documented story. And there's lots of other stories, too, so if AnnaSquirrel saw her squirrel using its thumb opposably, then there's another tally mark for those who think squirrels have thumbs. When you consider, wwh, the great achievements we human beings gained due to our having opposable thumbs, I'll bet our ability to touch our pinky with our opposable thumb doesn't rate very high in achievements. I mean, we aren't even using a very respectful name for that pinky here, are we.
Just to be argumentative and good night,
WW