Multiattack

The tyrannosaurus makes two attacks: one with its bite and one with its tail. It can't make both attacks against the same target.

Bite

Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 33 (4d12 + 7) piercing damage. If the target is a Medium or smaller creature, it is grappled (escape DC 17). Until this grapple ends, the target is restrained, and the tyrannosaurus can't bite another target.

Tail

Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 20 (3d8 + 7) bludgeoning damage.