Hyaenodons were huge rhino-sized running predators with enormously powerful jaws. The top hunters of their time, they lived on the grassless scrubby plains of Asia and North America. Smaller species would have hunted in packs, most often at night, using their powerful jaws to crush bones; the largest would probably have hunted alone. The males show grinding marks on their teeth— much like modern animals which use the noise of grinding teeth as an intimidation display. Fossilized dung also shows that they often defecated on carcasses to protect them from scavengers.