For me I tamed him on ark fjurdur in balheimr I used a argentavis to go to a high area and then I started shooting him with tranq arrows it took me like 14-15 tranq arrows then I gave him raw prime meat and then I tamed him. Hope this helped. Good luck for everyone taming him.
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.
Did you know that thorny dragons when they hit other dinosaurs 🦖 with their thorns on their tails, it actually knocks out the dinosaurs 🦕 not kill them, it mite kill the but most likely not and it takes from like 540 to at least 600!!