A sternal bone of plated ornithischian dinosaur Stegosaurus (Upper Jurassic, Utah), the first for Stegosauria, and the enigmatic "sternal bones" of Gilmore (1914)

Associated with a right scapula-coracoid of Stegosaurus from the Morrison Formation (Upper Jurassic) of the Carnegie Quarry, Dinosaur National Monument, Utah, is a right sternal bone, so identified by comparison with sternals of other ornithischian dinosaurs. Comparisons show that the three “sternal bones” of Stegosaurus identified by Gilmore (1914) from the Morrison of Como Bluff, Wyoming do not match sternals of any dinosaur. They are tentatively re-identified as the anterior half of the right ischium of a nodosaurid ankylosaurian dinosaur and a right and a left proatlas from a very large sauropod dinosaur. A sternal bone from the Cleveland-Lloyd Dinosaur Quarry, Utah is from a large non-Camptosaurus, non-Dryosaurus Morrison ornithopod dinosaur.