Reznor

Reznor is a group of four dinos on spinning platforms. They shoot out fireballs at you, hit their platforms from below to win. After you start to knock two of them off the platforms the floor will break away to make a gap over a lava pit.

They are found as the bosses of the many fortresses scattered through the areas of Super Mario World. Specifically, the fortress above the Vanilla Dome, the Forest of Illusion fortress, the Chocolate Island fortress, and the Valley of Bowser fortress.