|A male Klipspringer (Oreotragus oreotragus, from the Greek for "mountain goat")|
However, small size is not what makes these animals unique. As you can see in the image above, they have hooves like no other. While all hooved animals walk on their toenails, the klipspringer in the only species to walk on the very tip of their nails. This is why they have such an upright stance. Because of this as well as the structure of the hoof itself, these little antelope are quite agile, which serves them well in their rocky habitat. Their hooves are small--about the size of a dime--and they can easily stand with all four feet close together to perch on small rocky spires. Their graceful movement is often compared to ballet dancer, and their hooves to one dancing on point. Though this comparison is rather fitting, there is one small sticking point: ballet dancers on point are not dancing on their toenails.
Here's a video of a klipspringer at Rotterdam Zoo:
Sources are Animal Diversity Web, ARKive, Honolulu Zoo, and Ultimate Ungulate. Image is from Wikimedia Commons under a Creative Commons license. Video is from YouTube.com.