In ancient Roman religion and myth, Jupiter or Jove is the king of the gods and the god of sky and thunder. Jupiter was the chief deity of Roman state religion throughout the Republican and Imperial eras, until Christianity became the dominant religion of the Empire. He is usually thought to have originated as a sky god. His identifying implement is the thunderbolt, and his primary sacred animal is the eagle, which held precedence over other birds in the taking of auspices and became one of the most common symbols of the Roman army. The Romans regarded Jupiter as the equivalent of the Greek Zeus, and in Latin literature and Roman art, the myths and iconography of Zeus are adapted under the name Iuppiter. In Greco-Roman mythology, Jupiter was the brother of Neptune and Pluto. Each presided over one of the three realms of the universe: sky, the waters, and the underworld.