I got mine from hopping on beefed sarco shot it with tranq arrows on crossbow and with about 16-20 it was tamable so then throw prime or regular fish meat and should go easy as long as you have at least 30-45 narcotic or 15-20 biotoxin with you
I had a Spino once. His name was J.J. I loved him. But like always, good things always come to an end. We were out looking for giant turtles for their keratin when J.J. fell over the edge of a cliff. I was on my pteradon so I flew over the edge and J.J. was following me back to bace when he was killed my a therizinosaurus... I just sat there on my pteradon watching him be torn apart, unable to help... So now, my bace is called Fort J.J. in honor of him. I will always remember my most loyal friend.
While I was knocking this guy to tame him he suddenly ran away SO FREAKING FAST HE SHOVED HIS HEAD IN A CLIFF. Good thing he hit a cliff because if not, it would be day 1000 and me and my argy would still be chasing after him.
Whenever you're taking the Spino, remember to take at the very least 300 narcotics. It wakes up FAST, and whenever your taming ANY creature, surround it with wooden spike walls! Saves me countless tames from smaller pack animals. And to knock it, you simply need steep high ground and go to town with your tranqs. Happy taming!