Carl Zimmer in his blog, The Loom:
If you could travel back to Spain about ten million years ago, you’d have no end of animals to watch, from apes to bear-dogs to saber-tooth tigers. With so many creatures jockeying for your attention (and perhaps chasing you down for lunch), you might well miss the creature shown here. Simocyon batalleri was roughly the size and shape of a puma, although its face looked more like a raccoon’s. If anything were to draw your attention to Simocyon, it would probably be the animal’s gift for climbing trees. Most big carnivorous mammals of the time were restricted to the ground; some may have been able to climb up tree trunks and onto bigger boughs. But judging from its fossils, Simocyon could have climbed trees out to their slender branches. It could do so because, unlike other carnivores, it had thumbs that it could use to grasp branches much like a monkey would. Those thumbs turn out to have a fascinating story to tell about the tinkering habits of evolution.