Fossil

Fossils are square, stone objects found in Stonetooth Cave of Wario Land: Shake It!. The are produced from spawners onto Conveyor Belts, typically in a way that Wario must manoeuvre around them to pass. Some are positioned in such a way that they allow Wario to reach a conveyor switch, but one of the levels missions disallows touching them, forcing the player to find another way to reach the switch should they choose to obey it.

The fossil it seems to represent is an ammonite shell.