Hippocampus

Hippokampoi pulling Poseidon's Chariot

The Hippocampus is also known as the Sea-Horse, and these half horse/half fish creatures are found in Green, Phoenician, and Etruscan mythology.

These aquatic equines are depicted as having the bodies of horses, but the long, scaly tails of fish or serpents.   They were even sometimes drawn having fin-like manes. Some ancient people believed them to be the adult forms of actual seahorses, rather than a separate creature altogether.

17th Century Depiction

Interestingly, one of the first depictions of the Hippokampoi (the plural) was found within the hotly contested Lydian Hoard, a collection of 7th century BCE artifacts from Turkey that were once owned by the Metropolitan Museum of Art. A small golden Hippocampus was a part of this collection, though it was stolen around 2007 and has not yet been recovered.

Hippokampoi were the mounts of the sea nymphs and the steeds that pulled Poseidon's chariot (he usually used four of them). They have appeared in these roles through countless works of art spanning centuries. They were popular in bathhouse mosaics, they were used in heraldry during Medieval times by maritime families, and they continued to be painted and sculpted in the Renaissance and beyond. Winged Hippokampoi are even found in the famed 17th century Trevi Fountain of Rome.