Brontoraptor" (meaning "thunder thief") is the informal name given to a genus of dinosaur from the Kimmeridgean stage (around 150 million years ago) Upper Jurassic Morrison Formation. It was a tetanuran theropod which lived in what is present-day Wyoming, and may have been a megalosaur. "Brontoraptor" is not yet officially published, despite appearing as a nomen nudum in the 1990s. A manuscript describing it has been circulated online, and the name was coined by paleontologist Robert T. Bakker. Brontoraptor was very bulky and heavily built. Its bones were incredibly thick and it is thought they were mainly scavengers, due to its mass and the fact that it probably couldn't chase down prey.