Ankylosaurus(A.magniventris)

Unarmored Belly. If the Ankylosaurus is prone its AC drops by 3 and it loses its resistances.

Thumper. Ankylosaurus can use it's tail club to kick up earth. As an action the Ankylosaurus can slam its tail club into the ground, kicking, dirt, rock and particulates within a 10 ft radius from a space up to 10 ft behind it. Any creature in that space must make a DEX Save of 14. On a failed save, the creature takes 3d6 bludgeoning damage and is knocked prone. On a success, the creature takes half damage. Areas that have been hit with the tail club in this manner are considered difficult terrain.

Call for Help. If the Ankylosaurus is prone, or at half of its health or lesser, the Ankylosaurus can use a bonus action to let out a call for help. The DM must roll a d6. On a 1-2, the call is not heard, on a 3-4, the call is heard by up to one other Ankylosaurus, and on a 5-6, the call is heard by up to 2. Responding Ankylosaurus take a round to arrive and help.

Pack Tactics. The Ankylosaurus has advantage on attack rolls against a creature if at least one of the wolf's allies is within 5 feet of the creature and the ally isn't incapacitated.

Tail. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 18 (4d6 + 4) bludgeoning damage. If the target is a creature, it must succeed on a DC 14 Strength saving throw or be knocked prone.

Stomp. Melee Weapon Attack: +7 to hit, reach 5 ft., one target, 2 attacks. Hit: 29 (5d10+4). Ankylosaurus rears back onto hindlegs to bear down with two massive stomps on its opponents. If either Stomp attacks miss, it must make a DEX save against the DC of its missed attack. Failure causes the Ankylosaurus to fall prone.

Blind Flail. If attacked from behind, it can blindly lash out with its Tail making a melee attack with it at disadvantage and without its proficiency bonus.

Running of the Bulls. As an action, this creature can charge its movement speed in a single direction. All creatures in its path must make a DEX save of 14 and suffer 6d10 bludgeoning damage, half on a success, and are knocked prone. This has three charges. Charges are regained on a 5 or a 6 on a d6 rolled at the beginning of a round.