New way of getting primal crystal

Get them to aggro on you and make sure their head is in the middle of the Dino gate. Get a snow owl or mana (easier to tame on gen 2, good luck on lost island if you don’t have the DLCs). Freeze them and quickly go around the back and put another gate.

Wanna be more risky?

Try using the stegosaurus’ impale ability, if it works on the wyvern, it should land and walk to you.