Fact: Hyaenodons in real life were actually not even related to hyenas , their closest living relatives are pangolins(which also are not related in the slightest to raccoons, anteaters, aardvarks, armadillos or hedgehogs). And real hyenas despite appearances are actually not related to dogs or wolves, in fact their closest relatives are meerkats and mongooses and meerkats and mongooses' closest other relatives are cats and civets(also known as bearcats)
Usage in game:
1) tame aid- can preserve prime meat allowing you to tame carnivores with ease.
2) pack hound- I’d personally only recommend for packs of five and upward, but their ability to heal like Argents means they gain strength with every victory.
3) Pet- Their just cute.
Normally you can't tame the pack leader, so just get a pteranodon or argy, pick it up and drop it in a large area (like a separate section of your base). When you take it away from the rest of the pack, it removes its 'pack leader' title, allowing you to tame the highest level hyena of that pack.
Despite it's appearance, the real life hyaenodon was nowhere near related to actual hyenas, but it actually belongs to a group of prehistoric mammals, all extinct, that are believed to be most closely related to pangolins, which aren't related to anteaters or armadillos, for your information.