My brother and I built a stone cage 2 by 3 by 3 walls high and a stone Dino gate. Then use a megalosaurus to pick it up and put it inside be careful it drops sometimes trying to get in. Once inside will stick its head out and you can tame it easily. P.S. it can fit through doorways when trying to escape
Easiest and safest way to tame this is to lure it under water. They stop aggro and you can tame as you please. Just make sure you come up for air every once in a while. Also be sure the water is deep enough.
Full Ghillisuit, bug repellent, and balls of steel because these are scary to tame! They have the taming slot right behind their head about where the saddle would normally sit. Must approach from behind and only approach when feeding, stay away otherwise