You can do an extremely efficient xp farm with rexes, and im gonna explain you how 👍

1: tame two rexes, a male and a female

2: (opcional) get yourself an ovirraptor so It grabs the eggs

3: hatch the eggs

4: dont claim the baby Rex

5: get on the dino you want to upgrade and kill the baby rexes.

When your dino kills the baby rexes, It Will gain a lot of xp and you Will have a super dino 🤑🤑