Bonaconn

The Bonaconn is a creature from Medieval bestiaries. They resemble a bull or an ox with horns curving inward, and a horse-like mane. Their dung is acidic, and can be fired like a weapon.

Citations:

Bane, Theresa. Encyclopedia of Beasts and Monsters in Myth, Legend and Folklore. United States, McFarland, Incorporated, Publishers, 2016.