The forms in which the gods are shown, although diverse, are limited in many ways. Many creatures that are widespread in Egypt were never used in divine iconography. Others could represent many deities, often because these deities had major characteristics in common. Bulls and rams were associated with virility, cows and falcons with the sky, hippopotami with maternal protection, felines with the sun god, and serpents with both danger and renewal. Animals that were absent from Egypt in the early stages of its history were not used as divine images. For instance, the horse, which was only introduced in the Second Intermediate Period (c. 1650–1550 BC), never represented a god. Similarly, the clothes worn by anthropomorphic deities in most periods changed little from the styles used in the Old Kingdom: a kilt, false beard, and often a shirt for male gods and a long, tight-fitting dress for goddesses.