This version of this essay is entirely from memory, I have not taken the time to track down various references. Maybe I will do that sometime.

Traditionally the unicorn is a composite beast with the body of a horse, the legs of a deer, the beard of a goat and the tail of a lion and the single spiral horn springing from its forehead.

There actually are a couple of cloven footed hooved mammals with a midline horn, among the living ones we have the giraffe and its smaller cousin the okapi. Of course they both have additional paired horns and the midline horn is not twisted into a spiral. As even toed hooved mammals they also have limbs with a "divided foot" like a deer. Both now are found only in Africa and probably have little to do with the unicorn legend.

It has been suggested that the description of the unicorn is based on traveler's tales of the Indian rhinoceros, an enormous relative of the horse, which possesses a head that sort of resembles a horse, a single horn (but on the nose) and a short bare tail with a tuft of hair on the end. They are colored light gray, not white.

The spirally twisted along its long axis, enormous, single tooth of the narwhale was presented to the public as a unicorn horn in the middle ages. When I was a paleontology student at Berkeley we had a narwhale tooth in the osteology collection and it was indeed impressive. A beautiful smooth twisted ivory shaft tapering to a point. As I recall it was almost as long as I am tall and it was quite heavy. It has influenced my rendering of unicorn horns.

My unicorns are not just horses with horns. They are from the great clade of cloven footed mammals - perhaps the product of a radiation into gracile open grassland runners from the giraffe lineage, smaller and swifter, with higher crowned cheek teeth and thus deeper heads. Beasts from an alternative earth. They do consent to being ridden at times, but it is not easy to throw a bridle over that long horn.