"Brontoraptor" is the informal name given to a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

 from the Kimmeridgean stage

Faunal stage

In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...

 (around 150 million years ago) Upper Jurassic Morrison Formation

Morrison Formation

The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...

. It was a tetanuran

Tetanurae

Tetanurae, or "stiff tails", is a clade that includes most theropod dinosaurs, as well as birds. Tetanurans first appear during the early or middle Jurassic Period.-Definition:...

 theropod which lived in what is present-day Wyoming

Wyoming

Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...

, and may have been a megalosaur. "Brontoraptor" is not yet officially published, despite appearing as a nomen nudum

Nomen nudum

The phrase nomen nudum is a Latin term, meaning "naked name", used in taxonomy...

in the 1990s. A manuscript describing it has been circulated online, and the name was coined by paleontologist Robert T. Bakker

Robert T. Bakker

Robert T. Bakker is an American paleontologist who helped reshape modern theories about dinosaurs, particularly by adding support to the theory that some dinosaurs were endothermic...

. 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.