Multiattack

The spinosaurus makes one bite attack and two claw attacks.

Bite

Melee Weapon Attack: +13 to hit, reach 15 ft., one target. Hit: 34 (4d12 + 8) piercing damage. If the target is a Large or smaller creature, it is grappled (escape DC 18). When the spinosaurus moves, the grappled creature moves with it. Until this grapple ends, the target is restrained and the spinosaurus can't bite another target.

Claw

Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 22 (4d6 + 8) slashing damage.

Tail

Melee Weapon Attack: +13 to hit, reach 20 ft., one target. Hit: 21 (3d8 + 8) bludgeoning damage.

Frightful Presence

Each creature of the spinosaurus' choice that is within 120 feet of the spinosaurus and aware of it must succeed on a DC 18 Wisdom saving throw or become frightened for 1 minute. A frightened creature repeats the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the spinosaurus' Frightful Presence for the next 24 hours.