From the Super Mario Wiki
Bone Dragons are large, hydra-like dragon skeletons that Yoshis encounter underground in the game Yoshi's Story. Bone Dragons will usually be blocking the way, to get past them Yoshi will have to either throw Yoshi Eggs at its head, or Ground Pound it, either way takes three hits. In a couple of cases Yoshi will encounter a three-headed Bone Dragon, complete with a body. Each of the heads take two hits and Yoshi will get three Melons when it is defeated. Touching the body won't hurt Yoshi.
An underground cavern on Yoshi's Island, called the Bone Dragon Pit is also explored in Yoshi's Story; as its name would imply, the Bone Dragon Pit is infested with Bone Dragons. However, Bone Dragons are very uncommon enemies since they only appear in that specific level.
Super Smash Bros. Brawl has a Sticker of a Bone Dragon that raises the strength of attacks that involve biting by thirteen. It can only be used by Yoshi, Wario, Pokémon Trainer, and Wolf.
|| Yoshi's Story
|| [Bite] Attack +13
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