Mattermouth

Mattermouths are enemies found in the game Super Mario Galaxy 2 that resemble the skulls of Dry Bones. They also seem to resemble Bone Dragons. They are found in places such as the Haunty Halls Galaxy and Bowser's Lava Lair and eat away part of the ground, which regenerates after a few seconds. If Mario falls into the holes in the ground created by the Mattermouths, he will lose a life. Mario cannot destroy them, but he can stop them temporarily by stomping on their heads, which will turn them around and cause them to begin eating the ground in the opposite direction. If Mario is attacked by one of these enemies, he will lose one wedge of his Health Meter. The name Mattermouth is derived from the words "matter" and "mouth".

Trivia

 * Mattermouths are similar to the Super Mario 64 beta Blargg, that originally was supposed to be in the game but was removed from the game for unknown reasons.