Late Cretaceous dinosaurs from the Denver Basin, Colorado Author Kenneth Carpenter Department of Earth Sciences, Denver Museum of Nature & Science, 2001 Colorado Boulevard, Denver, CO 80205, U. S. A. Author D. Bruce Young Department of Earth Sciences, Denver Museum of Nature & Science, 2001 Colorado Boulevard, Denver, CO 80205, U. S. A. text Rocky Mountain Geology 2002 37 237 254 journal article 10.2113/gsrocky.37.2.237 41bd81a8-8d16-41cb-950f-8fab1660f845 3943081 Hadrosaurid genus and species indet. Figures 2 and 15 Agathaumas milo Cope, 1874a Cionodon arctatus Cope, 1874a Material. —AMNH 3951 (type of Cionodon arctatus' ) maxillary fragment, dorsal vertebrae, metatarsal III distal end, metatarsal IV proximal end (Laramie Formation, exact locality unknown, but believed to be Bijou Creek); DMNH 29475 tooth (Denver Formation, Loc. 20); DMNH 32828 tooth (Denver Formation, Loc. 20); DMNH 34341 tooth (Denver Formation, Loc. 20); DMNH 44600 right pubis (Denver Formation, Loc. 14); UCM 38059 tooth (Denver Formation, Loc. 37); UCM 42326 tooth (Laramie Formation, Loc. 1); UCM 42327 tooth (Laramie Formation, Loc. 1); UCM 43654 right femur (Laramie Formation; Loc. 3); UCM 437372 vertebrae (Laramie Formation, Loc. 6); USNM 7623 ungual (Denver Formation, Loc. 17); and footprints (Laramie Formation, Loc. 9, 10). Description and discussion.— Cope named Agathaumas milo in 1874a, but he did not provide a description of the material. Later, Cope (1874b) described the material under Hadrosaurus occidentalis . As Cope admitted, the material is very fragmentary, and his description is too incomplete for identification beyond family level. The material cannot be located now in the American Museum of Natural History. The holotype of Cionodon arctatus is also very fragmentary. It was figured by Cope (1875) and here in Figure 2 . The material is clearly hadrosaurian, but little else can be added to Cope's original description. Lull and Wright (1942) suggested that C . arctatus was “... evidently from the watershed between the South Platte River and Lodge Pole [sic] Creek, Colorado." However, the strata here are mostly mid-Tertiary in age (mostly the Upper Eocene-Lower Oligocene White River Formation) and are exposed as a broken line of cliffs just south of the Colorado-Wyoming border. Furthermore, Cope (in Cross, 1896) stated that the specimen came from Bijou Creek. The Laramie Formation along Bijou Creek is covered by a wide mantle of Quaternary sediment. It is not exposed until just north of Deer Trail, along East Bijou Creek, where it extends south for 60 km. Either the specimen came from this stretch of the Laramie, or the specimen actually came from the Denver Formation exposed along one of the other drainages, such as south of Strasburg. A hadrosaur pubis was found in 2001 near Strasburg in the Denver Formation (Loc. 14). The prepubic process is damaged and the postpubic process is incomplete. The prepubic process is estimated to be over 48 cm long. The femur ( Fig. 15 ) was collected by amateur paleontologist Asa Maxson in the early 1930s. It is 90 cm long, suggesting that it belongs to a subadult individual. Footprints believed to be of hadrosaurs have been described by Lockley and Hunt (1995) from the lower part of the Laramie Formation, which Weimer (1973) has interpreted as delta plain deposits. The prints are of different sizes indicating that their makers were individuals of different ages.