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.
Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 15 (2d10 + 4) piercing damage.
Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) slashing damage.