Bonacon

Pliny speaks of a creature, which he calls the bonasus, of Paeonia (in Asia), having the mane of a horse, but in all other respects the look of a bull, with horns so curled as to represent no danger, but capable of emitting excrement whilst running away, of such noxiousness that pursuers were scorched as if by fire.

Subsequent accounts have added a horse's tail to the mane, and poisonous gas to the excrement, and the variant name of bonacon.

For reasons of politesse, the SCA do not (currently) allow the bonasus/bonacon as an heraldic charge.