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.
This enormous predator terrorizes all other creatures in its territory. Despite its size and weight, a tyrannosaurus is a swift runner. It chases anything it thinks it can eat, and there are few creatures it won't try to devour whole. While prowling for substantial prey, a tyrannosaurus subsists on carrion, and on any smaller creatures that try to dart in to steal its meal.