Mega Feraligatr’s newly enlarged dorsal fin plays many useful roles.

For one thing, it offers a defensive boost. Mega Feraligatr can reduce the damage from incoming physical attacks by covering its head with that large, hard fin. It also helps the Pokémon dissipate heat better. Mega Evolution causes a rapid increase in body temperature. Mega Feraligatr can emit heat from its dorsal fin, cooling itself down.

For reasons unknown, Mega Feraligatr’s dorsal fin resembles Totodile’s head—leading some to call it a “Totodile mask.”

One theory suggests that Totodile’s head is shaped optimally for biting, and Mega Evolution gave Feraligatr this “Totodile mask” in order to restore its biting power. But it’s unclear whether this is true.