Need to travel on land? Andrewsarchus has you covered. Underwater? Andrewsarchus. Hazardous area? Lava? Radiation? Dismounting/stunning attack creatures? Andrewsarchus.
Passive tames that you can relatively easily get as early as literally level 1, and will probably be your primary mount the entire game. They can be ridden without a saddle, but the saddle is worth it. Equipped with a turret, functioning as a hasmat suit and a submarine, and fully protecting the rider from everything Ark can throw at you, this is easily the single best dino any survivor can tame.
Oh, and they can absolutely be boss killers if you enjoy super-breeding them.
The rider can NOT be dismounted, via that being voidwyrms, being picked up, or even a net gun. In fact, the net gun nets the Andrew, but the rider stays on and can shoot the attacker. Also you can Press c (or whatever button it is) to dash. The Andrew goes super fast but that’s not all, the dash also gets you out of the net INSTANTLY! Also did I mention that when stunned by a jelly or voidwyrm, it is NOT slowed down?!
For Xbox and PS5 players, click the left joystick ONCE to enter turret mode, hold to sprint/sink, or move the right joystick forward twice to sprint. Left trigger to kick, right trigger to bite/shoot. Was a pain to find out on Xbox.