Quora answer: What are single-hoofed horses in the Iliad?

Soliped Pictures and Definition

But we must not forget that the horse has a special place in Homer.

For instance there is the Trojan Horse

And there are the horses of Poseidon [See also POSEIDON : Greek God of the Sea & Earthquakes]

There are the immortal horses: HIPPOI ATHANATOI

And there are the brothers of Helen who were famous as horsemen: Castor and Pollux

So the fact that the Horse had a single hoof was a way of calling it out and giving it dignity over other animals.