Pros: you can bury them underground and put them on passive for a hidden storage box. You could bury them and put them on neutral or aggressive and when you get raided your enemies won't even have a clue what hit them.
They knock enemies off mounts and stun them.
They do crazy damage.
Cons: sometimes I even have a hard time remembering and finding where I buried them.
How to tame: find one that's already attacking something, when it wins the fight lure it into a dino trap and tame it. (If its badly injured give it time to regain health before taming).
Otherwise If you try looking for one under the ground it will stun you and most likely kill you.
Craft ghillie armor and four dinogates with gates. Find a mine shaped pile of mud in snow area. Kill everything dangerous in the area. Crouch and place dino gates around the mound. The purlovia cant escape the pen now. Ghillie armor very important so you can place gates without it seeing you.
Take Care when searching with flying Mounts for Ovis. They can throw you Off and Paralyse your bird for several seconds. In combination with Packs of wolves this can be your and the birds Ende. I am speaking of experience.
When they are Buried you May See a small mountain.