Name Meaning: Cenozoic beast
Geologic Era: Oligocene-Early Miocene
Location Discovered: France
Size: 30 cm long (about 1 foot)
Estimated Range: Europe
Extinction Date: Early Miocene
Cainotherium was a small herbivore found during the Oligocene era. At first glance, this animal resembles the rabbits found now. Well developed hind legs would have been well suited to jumping or bounding. Large ears would have lent Cainotherium excellent hearing, an essential trait in what would have been a prey animal. The auditory centers of Cainotherium’s skull are comparable to that of modern rodents, which again suggests large ears and a good sense of hearing. The impression is a small, fast animal that would not look out of place in a modern vegetable garden.
A closer look at Cainotherium’s limbs shows some key difference from modern rodents and rabbits. Cainotherium had didactyl feet, meaning two toed. The other two toes on each foot were still present, but much reduced and moved up to the lateral side of each foot. They were reduced to the point of being non-functional, leaving the primary two digits as the walking and running surface. Cainotherium is actually more closely related to modern camels and horses, though is not a direct ancestor of either.
Our jaw fragment, while small at only a few centimeters in length, is nevertheless very well preserved. The teeth in particular still have very noticeable cusps, which would have been well suited to grinding plant life to a digestible pulp. Modern rodents tend to have a gap between the canines/incisors and the molars. Cainotherium had no such gap, and had a full complement of teeth. The skeleton above overall shows more resemblance to modern hoofed animals than it does to rodents.
Despite its seeming success throughout the Oligocene, Cainotherium leaves behind no direct descendants. This group of animals does not appear to have spread outside Europe, though the land bridges that still existed at the time would have allowed it to do so. All that is left of Cainotherium is skeletons and rather distantly related animals such as camels.
Skeleton and Life Reconstruction: Savage, RJG and Long, MR. Mammal Evolution: An Illustrated Guide. Facts on File Publications, New York. 1986. Page 214