So heres my tip for noobs that want a rex

1st. 30 tranq arrows

2nd. A crossbow

3nd. A high cliff that the rex cant get to

Now after u find a really high ciff that u can still shoot the rex but the rex cant get you

Shoot it

Then feed it raw prime meat

I prefer using a theri to getting meat cuz its ez to make things extinct in hervivore island

Boom u now have a evovled murder ostritch