Triceratops
Many fossils of Triceratops have been collected since the genus was first described in 1889. There is at least one complete individual skeleton. Paleontologist John Scannella observed: "It is hard to walk out into the Hell Creek Formation and not stumble upon a Triceratops weathering out of a hillside". Forty-seven complete or partial skulls were discovered in just that area during the decade 2000–2010. Specimens showing life stages from hatchling to adult have been found.