Before Poseidon was known as the god of the sea, he was linked to the horse and may have originally been depicted in equine form. This connection reflects the violent and brutal nature of Poseidon the earthshaker, the bonding of horses and springs, and the psychopomp character of the animal.
Neptune, in contrast, has no such direct connection to horses. The Roman deity Consus was associated with the horse, and his underground altar was in the valley of Circus Maximus, at the foot of the Palatine (place of horse racing). In Consualia summer (21 August) it was customary to bring horses and mules, crowned with flowers, in procession and then to hold horse races at the Circus.
The festival also traditionally re-enacted the abduction of Sabine (and Latin) women, reflecting the sexual license characteristic of such festivals. On that day, the Flamen Quirinalis and the Vestal Virgins made sacrifices at the underground altar of Consus. The proximity of the two Consualia to the Opiconsivia (the latter were four days later, the winter festival on December 19) indicates the relationship between the two deities referring to agriculture.
According to Dumézil, the horse has a very different symbolic value in the theologies of Poseidon and Consus. Tertullian (De Spectaculis V 7) wrote that, according to Roman tradition, Consus was the god who advised Romulus about the abduction of the Sabines.