0.45" (1.15 cm) diameter Stegosaurus Gular Scute (Neck Armor) from the Morrison Formation found in Moffat County, Colorado.  Stegosaurus had many of these small neck scutes on the underside of their neck. Even though Stegosaurus is a very well-known dinosaur their fossils are relatively uncommon in most Morrison quarries. 150 Million Years Old.