Build 5 stone dinosaurs gateways in a circle with 2 pillars in the middle of each doorway except 1, lead the desired tame through the gates with 1 pillar and as he's stuck, put one on top of the first pillar trapping him.
Try to make them fall into a ravine. Flyers help with this tactic. Or better, look for some that spawned or fell into one. There’s a ravine on my SP game where there are around 11 allos that fell into it. After getting them into a ravine, kill off all but the one you’d like to tame. Proceed in taming as usual.