Poseidon&Neptune
Sea, Storms, Earthquakes, & Horses
Poseidon
Earth-Shaker, Enosichthon
Trident, dolphin, horse, bull, pine
A pre-Olympian Mycenaean Poseidaon, likely a chthonic earth-lord before becoming a sea god.
Tempestuous, resentful, territorial — quick to drown sailors and flood cities.
Black bulls drowned at sea and the Isthmian games' horse-racing rites.
The sea's indifferent violence, negotiated with but never trusted.
Neptune
Neptunus Equester
Trident, dolphin, hippocamp, horse
An early Italic freshwater and horse-racing god who absorbed Poseidon's oceanic portfolio late in the Republic.
Cooler and more remote — a patron of horses and naval security rather than of storms.
The Neptunalia's rustic arbours and the cavalry's equestrian offerings.
Water as infrastructure: the sea as a Roman lake to be policed.
Syncretism Analysis
Poseidon is the ocean's rage made divine; Neptune began as a freshwater and cavalry deity and only later inherited the trident. Rome cared less for the god's temper than for command of the waters it sailed.