Hold Breath. Spinosaurus can hold its breath for 30 minutes.

Infected. The Spinosaurus can infect a dinosaurs with the plaque and turn that dinosaur into a zombie 

Multiattack. The Spinosaurs 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. 

Claw. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) slashing damage.

Undead Nature. A  Spinosaurus zombie doesn't require air, food, drink, or sleep.