Sandworm
From Sonic Retro
Sandworm, called Nal (ナール) in the Japanese Manual, is a caterpillar badnik from Sonic & Knuckles found in the quicksands of Sandopolis Zone. They swim around in the quicksand and jump out of it to attack the player. They are very similar to the Caterkiller in terms of appearance, including having the same name in Japanese, but differ in the palette and behavior. But just like the Caterkillers, they can only be destroyed by jumping on their noggins.