All I had to do was take a Pteranodon to Y30, X80 and there were a lot of Argentavis' there get off your Pteranodon and use it as a distraction, Trank the Argentavis until knocked out I suggest putting some levels into health on the Pteranodon if you want it to survive, use prime meat or normal meat to tame it it's really easy and it's a great bird to have