Location : Western U.S.

Nanotyrannus is known from a single skull and jaw. The skull was originally thought to be that of an Albertosaurus  but significant differences were noticed years after it had been prepared and stored on a museum shelf. The skull was re-prepared, studied and re-described by Dr. Robert Bakker. Nanotyrannus had the honor of being the first dinosaur to be CAT scanned.

Nanotyrannus had forward-facing eyes like T. rex, which gave it very good depth perception. It had sharp, serrated teeth and powerful neck muscles. Combined, these tools would have made it an excellent hunter.

Some paleontologists believe that Nanotyrannus is a juvenile Tyrannosaurus  rex, partly because some of the skull bones are not fused, indicating an immature animal. A few paleontologists have suggested it may be a type of huge dromaeosaur (raptor).