" Like its master, it was entirely devoid of hair, but was of a dark slate color and exceeding smooth and glossy. Its belly was white, and its legs shaded from the slate of its shoulders and hips to a vivid yellow at the feet. The feet themselves were heavily padded and nailless, which fact had also contributed to the noiselessness of their approach, and, in common with a multiplicity of legs, is a characteristic feature of the fauna of Mars. The highest type of man and one other animal, the only mammal existing on Mars, alone have well-formed nails, and there are absolutely no hoofed animals in existence there. "
― Edgar Rice Burroughs , A Princess of Mars (Barsoom, #1)