Dinosaurus Rox

Dinosaurus Rox, also known as the Rock Boss, is currently the only boss in the game, at the end of both the yellow caverns and the red caverns.

How to defeat
You can only deal damage to him by attacking the large red tip of his tail. You can get around by moving close enough to him, so that he rears up for a smack. Then quickly dodge to your left, and his tail will turn towards you as he misses his attack. It will take a few hits to take him down. If you have a jetpack and can fly above him, you can get behind him while he swings to potentially get an extra hit in before he resets.