According to Cumont, the imagery of the tauroctony was a Graeco-Roman representation of an event in Zoroastrian cosmogony described in a 9th-century Zoroastrian text, the Bundahishn. In this text the evil spirit Ahriman (not Mithra) slays the primordial creature Gavaevodata, which is represented as a bovine. Cumont held that a version of the myth must have existed in which Mithras, not Ahriman, killed the bovine. But according to Hinnells, no such variant of the myth is known, and that this is merely speculation: "In no known Iranian text Zoroastrian or otherwise does Mithra slay a bull."