He is of godly origin, but it all went a bit pair-shaped. DEMETER, trying to flee from the advances of POSEIDON, changed into the form of a mare. A bad move as the Sea God had invented horse-racing and soon caught up with her in the form of a stallion.
Then it was up! and over! Apart from the subsequent birth of a black-maned horse and a nymphly daughter. The horse was called ARION and he has a slight handicap: human feet on his right hand side. This must cause many problems when it comes to horseshoes.
He can also speak, although we suspect that most of what he has to say is unprintable.
Another version of the story claims that his mother is the screamingly spiteful ERINYS. If so, we hope the anti-animal-cruelty organisations are standing by.