[D] Agathaumas sylvestris [sG] [T]
Cope , 1872
Cretaceous Late Maastrichtian
Ornithischia Genasauria Cerapoda Marginocephalia Ceratopia Neoceratopia Nomina Dubia
1 mile south of Black Butte railroad station, Sweetwater County, Lance Formation, Wyoming, US
Partial sacrum and pelvis Cope originally classified the form as a hadrosaur and did not recognize the genus as a horned dinosaur until Marsh described Triceratops in 1889. Cope later proposed that both Triceratops and Monoclonius were junior synonyms of Agathaumas.
Charles R. Knight\\\'s fanciful 1897 painting of Agathaumas, done under Cope\\\'s guidance, combined Marsh\\\'s skeletal reconstruction of Triceratops prorsus with a long straight nasal horn that Cope previously had identified as Monoclonius sphenocerus (the spectacular horn may come from a Styracosaurus).
Knight also depicted the supposed \\\"dermal armor\\\" that Marsh mistakenly attributed to Triceratops, material now identified as spikes from the skull of the pachycephalosaur Stygimoloch and scutes from an unidentified ankylosaur.