You don’t need to trap this to tame, it’s a solo tame. If you run up to it, it will go into turret mode then you need to walk circles around it and keep hitting with tranq until it eventually tries to walk away *in turret mode so really slow walking*
Make a 2x2 cage with ramps and a door. Lure the velonasaur in with a flyer. If you stay close to him he won’t enter turret mode. Leveling melee raises his projectile hit points. Also level stamina to attack longer. A high level can shred everything I’ve come across. Can’t wait for an imprinted one for the speed bonus.
These should be your first tame since there saddle is unlocked at level 27 in extinction also they can shoot faster then an automatic turret also I've just read this they can block turret bullets so I hope they can damage tek turrets with there needles or out gun all turrets.