The Hippocampus, thought by ancient Greeks to be the adult form of the seahorse.
They pulled Poseidon's chariot through the seas.
On a side note, a lucrative freelance gig helped me to save a nice sum of money.
At an art fair, I saw a fantastic carving of a Hippocampus, like you would find on a carousel. Tempted to buy it, the Voice of Reason told me to use the money instead as a down payment on my first house.