Mounted specimen from the The Museum of Paleontology, Russian Academy of Sciences, Moscow.
When: Miocene to Pliocene (~16 to 8 million years ago)
Where: Europe, Asia, and Africa
What: Chalicotherium is a member of the Chalicotheriidae, a bizarre group of animals, which resemble a cross between a horse and a gorilla. This group is unique among its relatives for having much longer front legs than hind, and it is the only ungulate to walk on its knuckles. Chalicotherium stood roughly 8.5 feet (~2.6 meters) tall at the shoulder, and was able to reach much higher than this into the tree tops via its long arms. Its posture served to protect the large claws on its hands, which allowed it to easily pull down leaves and branches. Its dentition suggets this was its primary, if not only, food source, it does not appear to have fed at all on the grasses which were starting to spread at this time. Chalicotheres are related to horses, in the order Perissodactyla; within this order they are more closely related to living rhinos and tapirs, to the exclusion of horses.
Let me add that this animal has always freaked me out a bit! Sure, I have seen lots of bizarre fossil forms, but for some reason the mix of a gorilla and a horse that stood almost 9 feet tall hits all the wrong buttons. I am a bit glad this one is extinct. ;)