A hyaenodon.
Hyaenodons are large, carnivorous mammals with a canine resemblence. They were not very intelligent creatures, as proven when they had trouble speaking to the rogue Felid, Carnassial, and when they did speak their grammar was very primitive. To make up for their lack of intelligence, Hyaenodons were powerful creatures working in a pack made of a small number that took their prey down with brutal strength.