Monster Manual, p.79
Pounce. If the Allosaurus moves at least 30 feet straight toward a creature and then hits it with a claw attack on the same turn, that target must succeed on a DC 13 Strength saving throw or be knocked prone. If the target is prone, the Allosaurus can make one bite attack against it as a bonus action.
Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 15 (2d10 + 4) 2d10+4 piercing damage. Claw. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) 1d8+4 slashing damage.
The Allosaurus is a predator possessing great size, strength and speed. It can run down almost any prey over open ground, Pouncing to pull the creature down with its wicked claws.
Grassland