These guys are the worst. You wouldn't expect a herbivore to aggro on you from just even breathing near it. If you're a low level player and you have a trike, mount on the trike and use their knockback to kite these jerks until they die or you die. Their high damage output, torpor-inducing attacks and quick deterioration to armor durability means engaging one in a melee fight is almost suicidal unless you are in a possession of a melee weapon that can kill one in a few hits and good armor that's above on par or better than the armor value of riot armor.

Recommendation: Use a large mount like a Spino or a Rex to kill them. You can kill them quicker if you own a tamed Giganotosaurus and a Rocket Launcher.