<P> In a late 2nd century AD floor mosaic from Thysdrus, El Djem, (illustration) Apollo Helios is identified by his effulgent halo . Another haloed Apollo in mosaic, from Hadrumentum, is in the museum at Sousse . The conventions of this representation, head tilted, lips slightly parted, large - eyed, curling hair cut in locks grazing the neck, were developed in the 3rd century BC to depict Alexander the Great (Bieber 1964; Yalouris 1980). Some time after this mosaic was executed, the Emperor began to be depicted with a halo, which was not abandoned when they became Christian; initially Christ only had one when shown on a throne as Christ in Majesty . </P> <P> The halo was incorporated into Early Christian art sometime in the 4th century with the earliest iconic images of Christ, initially the only figure shown with one (together with his symbol, the Lamb of God). Initially the halo was regarded by many as a representation of the Logos of Christ, his divine nature, and therefore in very early (before 500) depictions of Christ before his Baptism by John he tends not to be shown with a halo, it being a matter of debate whether his Logos was innate from conception (the Orthodox view), or acquired at Baptism (the Nestorian view). At this period he is also shown as a child or youth in Baptisms, though this may be a hieratic rather than an age - related representation . </P> <P> A cruciform halo, that is to say a cross within, or extending beyond, a halo is used to represent the persons of the Holy Trinity, especially Jesus, and especially in medieval art . In Byzantine and Orthodox images, inside each of the bars of the cross in Christ's halo is one of the Greek letters Ο Ω Ν, making up ὁ ὢν--"ho ōn", literally, "the Existing One"--indicating the divinity of Jesus . At least in later Orthodox images, each bar of this cross is composed of three lines, symbolising the dogmas of the Trinity, the oneness of God and the two natures of Christ . </P> <P> In mosaics in Santa Maria Maggiore (432 - 40) the juvenile Christ has a four - armed cross either on top of his head in the radius of the nimbus, or placed above the radius, but this is unusual . In the same mosaics the accompanying angels have haloes (as, in a continuation of the Imperial tradition, does King Herod), but not Mary and Joseph . Occasionally other figures have crossed haloes, such as the seven doves representing the Seven gifts of the Holy Spirit in the 11th century Codex Vyssegradensis Tree of Jesse (where Jesse and Isaiah also have plain haloes, as do the Ancestors of Christ in other miniatures). </P>

Most examples of early christian sculpture created before the 4th century are