To tame this bad boy is very easy, i will tell you the most easiest way to tame more then one if you want!
1 build a raft
2 build a cage on the raft that is made of stone. Build 6 rock foundations in the front of the raft then build 3 stone roofs for the floor, because this part will hang over the raft then build the three front walls on the on the raft with stone door frames, do not build on the side you drive the raft leave that only 2 door frames high! Then build the ramp to from the low back part then you have completed your portable Trex trap!
3 look for a Rex on the beach or close by
4 then lead the rex in your trap
5 tang it and tame it!
The reason you build the portable trap is you can take it back to base and tame it there so that way you have all your resources in one place to tame it good luck!