The Bone Dinosaurs are mini bosses found in Dino Mountain. They are the resurrected skeletons of ancient dinosaurs, revived by Topo, the crow boss of Dino Mountain. Each time you defeat one, a new passage opens allowing you to progress through the stage.
The Bone Dinosaurs have bodies made of magma, and as such eggs are ineffective against them. You must use the attacks of monsters, the ice attacks of Richie being the best for the job. They throw flaming rocks into the air, which can hurt you, so you must dodge them. A couple solid hits from Richie should be enough to defeat them