"And your snores would waken a stone dragon- yet we thank you."

—Elves of Rivendell speaking to Bilbo Baggins in The Hobbit

Stone Dragons are a breed of dragons mentioned once in The Hobbit. Nothing is known about them and they might be an imaginary creature in Middle-earth instead of being a real creature, similar to the Were-worms. Another possibility is if they are not a different breed, they are another name for Cold-drakes. Weta Workshop's Cave-Drake might have been based on this dragon.