Very easy to tame if you know what your doing. First tame an Ichthyosaur. Then grab a crossbow and some tranq arrows and find one and knock it out. It is not be able to attack if you are on the Ichthy. As you are taming it, be sure to remain on the Ichthy unless feeding narcs, so other creature don’t hurt you.
Bring more tranq arrows then you think! Mine took 100 at close range, on the body, at LEVEL 3.
I took cooked prime meat (stays better longer) and got mine in only four feedings. On an icthy they don’t chase (mobile player here) happy taming- Survivor Belle
Just tamed a 140 X Dunky. Yeahhh, really recommend that you build a trap for these peeps, spent 40+ mins trying to knock out this bad boy with a decent crossbow all while dodging tussos ect. Good times, stressful but good.