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.
I used a combat argy to follow them around till they got stuck on something. Tamed a 145 and 150 both times they just walked in place while I sat there and hit E every 30 secs. Don't leave the argy to close or they will continue to try and flee even while stuck.
In order to tame one in a pen you must have a another one of a higher level in separate pen nearby. The pens must be close enough that they'll receive a pack bonus, but too close and the alpha will prevent you from taming the beta.
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.