Aerodactyl

Fly-By. Aerodactyl doesn't provoke opportunity attacks when it flies out of an enemy's reach.

Fossil Fortitude: If damage reduces Aerodactyl to 0 Hit Points, it must make a Constitution saving throw with a DC of 5+the damage taken, unless the damage is radiant or from a critical hit. On a success, Aerodactyl drops to 1 hit point instead.

Multiattack. Aerodactyl makes one Iron Tail attack and one Crunch attack.

Iron Tail. Melee Weapon Attack: +6 to hit, reach 5 ft., 1 target. Hit: 13 (2d8 + 4) bludgeoning damage and the target must make a DC 14 Strength saving throw or fall prone.

Crunch. Melee Weapon Attack: +6 to hit, reach 5 ft., 1 target. Hit: 15 (2d10 + 4) piercing damage and the target must make a DC 14 Constitution saving throw or be stunned until the end of their next turn.

When Aerodactyl reaches below half of its maximum HP, it Mega Evolves into Mega Aerodactyl.