5. In fact, to Xerxes a fox born of a mare was a portent for the destruction of the empire. A monster to which a woman gave birth, whose upper body parts were human, but dead, while its lower body parts came from diverse animals, yet were alive, signified to Alexander the sudden murder of the king – for the worse parts had outlived the better ones. However, those monsters that are produced as omens do not live long – they die as soon as they are born.
The Etymologies of Isidore of Seville
Book xi The human being and portents