Placophanes (Info in comments)

nice info

look again

HP: 70,000
Defense: 50% on Back, 96% on Face and Arms
Attack: 5,000 in water, 7,000 on Land due to weight and gravity
Weak Point: Back, eyes, tail
Moves: Swipe (700 dmg) , Bite (5,000 dmg) , Tail whip (75 dmg), Heatbutt (Only available in water, 3,000 dmg)
Powers: Amphibious, 11,00 pound bite force (8,000 pounds per square inch), Crystaline Battering Ram, Crystaline Arms, Vortex, climbing
Arena name: Devonian Deathring
Arena Hazards: Small sharks, small placoderms, aggressive insects/arachnids, ammonites, predatory fish, rays, drowning

its whole body is its tail

You forgot about the five different crabdrones I have