Multiattack

The tyrannosaurus makes one Bite attack and one Tail attack. It can't make both attacks against the same target.

Bite

_Melee Weapon Attack:_ +8 to hit, reach 10 ft., one creature. _Hit:_ 31 (4d12+5) piercing damage. If the target is a Large or smaller creature, it is grappled (escape DC 16). Until this grapple ends, the target is restrained, and the tyrannosaurus can't Bite another target.

Tail

_Melee Weapon Attack:_ +8 to hit, reach 10 ft., one creature. _Hit:_ 23 (4d8+5) bludgeoning damage.