Neptune's legends seem to have formed after the Greek Poseidon, and draw heavily from the Poseidon lore. Poseidon, the god of the sea, was the son of Kronos and the brother of Zeus and perhaps Hades. When the world was divided, Zeus took the sky, Hades took the Underworld, and Poseidon took the seas. Although he is shown with a human body, Poseidon was able to live on land or under the sea. Poseidon was also the father of Triton, one of the most famous mermen in history.
Triton has the upper body of a man and lower body of a fish.
In art, he is usually shown rising from the sea, blowing on a conch shell. Triton's mother was Amphitrite, queen of the sea and one of the fifty Nereids. One of the earliest mermaids was Syria's Atargatis, loosely related to Astarte and Aphrodite, and perhaps to Pisces. She is also shown with a sheaf of wheat arched over her head, relating to a plentiful harvest. Other early literature describes similar creatures, including sea nymphs and perhaps Sirens.