Hyaenodon was a giant/huge creodont that lived in the oligene time period.
Hyaenodon were the size of a modern day rhino and attacked and ate Chalicotherium, juvenile Indricotherium and entelodonts. It was a carnivore. It evolved from creodonts, that lived during the Eocene epoch. Although it might look like Smilodon, the saber toothed cat, it was not related to it.
In Other MediaEdit
Hyaenodon appeared in walking with monsters: episode 3, Land Of The Giants. It was the main antagonist of the show.