Its best to knockout from up high where you are out of reach as it has quick attacks and decent damage. It does have a ranged topar attack as well but is easily dodged. Tranq darts are always the best option but if not available, delay your shots with tranq arrows by 2 to 5 seconds to allow the topar to build all they way. That way the arrows dont accidentally kill it.
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!!