Find a high lvled one, equip a few stacks of bolas.

Let it walk up n feed it element, you'll need roughly 20 element per 150 ferox, when it's done transforming, bola it right away, the bola will last throughout the whole transformation and when it's over you can feed it again, repeat til its tamed, be aware of carnivores around you tho, there you go, an supereasy way to get yourself the new op dino. Thumbs up folks!