Hippocamp

The Hippocamps are a species of hybrid creatures found in ancient mythology.

Description
The hippocamps have equine front body with forelimbs, and a long fish-like or serpentine tail. In adult form they are about the size of a large horse. Sometimes their hooves are depicted as webbed, and their mane is formed out of fins. Early art even has the hippocamps scaled like fish. Although hippocamps typically live in the salt water seas and oceans, they are also capable of surviving in fresh water, too.

History
Pre-dating even the Greek mythology, the Etruscans had hippocamps as an ancient myth. Belief in their existence was so prevalent that these sea-dwelling horses were regarded as natural creatures instead of divine origin. As such they are generally not thought to be originally born out of a god or an union between a god and another divine or mortal being.

In Greek mythology, hippocamps are often seen as mounts for gods and other sentient creatures of the sea. Poseidon and Triton have their chariots drawn by hippocamps, and Oceanid Nymphs called Nereids were often seen riding these mythological animals.

Trivia
Sea-horses were believed to be a juvenile form of this creature