If I wanna tame a thorny dragon when u only have a bow and arrows or slingshot is get on a high rock and when they shoot press C of X to hide from the spikes that do torpor and keep shooting it with trank's
If you are going to tame one of these with no dinos, be sure to upgrade your movement speed and get tranqs. When you see it whip its tail forwards move to the right you will dodge the shots. This worked for me.
If you have a wyvern or argy, easiest way I found to tame is to set up a taming pen, 2x4 with single door frames on the first level, walls on the second(stone), with a Dino gate on one end. Go pick up your dragon of choice and drop it in! Super easy and quick.