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)
If you can try and to lead them to a deep place of water since they will swim above the water and then just pet them from underneath you will be able to tame more too because the are unable to swim fast
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.