Lanmolas

They first apeared in The Legend of Zelda.

The three Lanmolas guarded the Pendant of Wisdom in the second dungeon of A Link to the Past. They dig out of the floor somewhere in the room, then fly a while and dive back into the sand. In this time they can be hit on the head or tail with Ice Rod, Arrows or Sword. However, it's harder to hit them with Arrows and Ice Rod. After they are defeated, Link gets the Pendant of Wisdom and a Heart Container.

Later in Ganon's Tower they guard the way up.

One did appear Link's Awakening as a mini-boss. It has guarded the Angler Key.

Note
This boss is posibly realated to Twinmold from Majora's Mask.