Great Basin Naturalist Volume 45 Number 4 Article 7 10-31-1985 Three new sauropod dinosaurs from the Upper Jurassic of Colorado James A. Jensen Brigham Young University Follow this and additional works at: https://scholarsarchive.byu.edu/gbn Recommended Citation Jensen, James A. (1985) "Three new sauropod dinosaurs from the Upper Jurassic of Colorado," Great Basin Naturalist: Vol. 45 : No. 4 , Article 7. Available at: https://scholarsarchive.byu.edu/gbn/vol45/iss4/7 This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. THREE NEW SAUROPOD DINOSAURS FROM THE UPPER JURASSIC OF COLORADO James A. Jensen' Abstract. — From 1972 to 1982 three exceptionally large sauropod scapulocoracoids and other ecjually large sauropod bones were collected from the base of the Brushy Basin Member of the Upper Jurassic, Morrison Formation, in western Colorado. Two of the scapulae are conspecific, but the third represents a second genus and possibly a new family. The two conspecific specimens are described here as; Supersaurus vivianae, the second genus is described as Ultrasaurtis mcintoshi, and a large, robust anterior dorsal vertebra of unique form is described as Dystylosaitrus edwini. Various miscellaneous elements are referred to the three genera. Historical tively new dinosaur fauna, described as the Uncompahgre fauna (Jensen, in preparation). The genus Brachiosaurus, named by The author later returned to Potter Creek and E. S. Riggs (1903), was part of an articulated collected additional brachiosaur material (be- skeleton the Upper Jurassic Morrison from ing described elsewhere). Formation within the present city limits of Grand Junction in western Colorado. Riggs believed the genus represented a land- Dry Mesa Quarry dwelling animal, rather than one preferring an aquatic habitat. Three large sauropod scapulocoracoids No one took him seriously at the time, but were collected from one of the Jones localities modern interpretations of sauropod habits near Dry Mesa, Mesa County, 35 miles west and paleoenvironments agree with him. The of Delta, Colorado. Over a period of 10 years brachiosaurs are now considered to be the the site proved to be very productive, yield- largest terrestrial animals to have lived on ing many tons of field blocks and packages of earth. dinosaur material. It was named after Dry The first uranium boom during World War Mesa and is located near the base of the II triggered the discovery of the second Brushy Basin member of the Morrison For- known North American brachiosaur; it was mation and, consequently, is not easily con- found by prospectors Eddie and Vivian Jones fused with the overlying Lower Cretaceous, who were looking for uranium, circa 1943, Cedar Mountain Formation when making when they collected a brachiosaur humerus simple stratigraphic determinations. The top from the Uncompahgre Upwarp and donated of the Morrison Formation is easy to follow it to the Smithsonian Institution, where it was cross-country because the superior Cedar put on display. However, no credit was given Mountain sediments are set-back above it, to the collectors. forming a prominent shoulder from 100 to 500 That display led to the discovery of the m wide. Sag-ponds are a characteristic feature Uncompahgre fauna and the materials des- of this shoulder, being produced by land-flow cribed herein. The author saw the Jones and slumping that crush and mutilate fossils humerus in 1958 and later in Colorado found contained in the moving sediments. Its ben- the Jones family, who took him to the location tonitic clays and mudstones, interbedded on Potter Creek. They also took him to three with soft sandstones, grits, and fine gravels, other major fossil localities on the Uncompah- respond actively to cyclic wet/dry stressing, gre Upwarp that together produced a rela- accelerating the deterioration rate of fossil Earth Science Museum, Brigham Young University. Provo, Utah 84602. Present address: 2821 North 700 East, Provo, Utah 84604. 697 posterior dodorsal vertebra, BYU B, Holotype, Ultm.saurus nmcintoshintoshi , F ig 1 A Brac/iK««,iru.ssp., dorsal vertebra. phalanges. anterior dorsal vertebra, BYU 5750. D, El, unidentified manual 50003. C, Holotype, Di/.s^r/Z.^n/n/scf/a/rH-, New Sauhopod Dinosaurs 699 )ctober 1985 JENSEN; anterior view. E, posterior view. 700 Great Basin Naturalist Vol. 45, No. view^'c; "''''"^'' ''"'^^^''"'- Jt;^i ^^^--^^J vertel,ra: SS";p!!;rr • A left /W later .1 km . October 1985 JENSEN: New Sauropod Dinosauks 701 materials beyond that of calcified sandstone or "glenoid process"; ridge separating the two limestone preservations. muscular fossae and running on a curved diag- One of the most important problems yet to be onal line up from the glenoid process to the solved is that of the exact age of the Dry Mesa maximum scapidar width is the "transverse sediments. It is mapped as Morrison Formation, ridge." This ridge and the shaft-axis form an but the fauna does not match taxa of classical angle that varies in different sauropod genera. Morrison localities. The assemblage is not only The great depressions to the left (above) and verv diverse but contains many taxa previously right unknown in the Upper Jurassic of North Amer- (below) of the transverse ridge are the ica. "superior fossa" and "inferior fossa," respec- The author believes the Morrison sediments tively. exposed along the eastern monocline of the Un- Description.— (Holotype BYU 5500; right compahgre Upwarp are younger than the Mor- scapulocoracoid) Scapula long but not robust; rison in previously described localities, and that distal end expanding moderately; shaft not the Uncompahgre fauna may represent the last severely constricted in midsection. expression of Jurassic dinosaur evolution. A shallow outward curve in inferior border slightly proximad to greatest width of scapula, at Class Reptilia top of transverse ridge, indicates origin of a liga- Order Saurischia ment, possibly M. scapulohumeralis. This pro- Suborder Sauropodomorpha cess also present on Diplodociis , occurring con- Infraorder Sauropoda siderably higher up on Cetiosaurus and most Family indeterminate prominently developed on Ultrasaurus , but ab- Supersauriis vivianae, n. gen., n. sp. sent or insignificant in Brachiosaunis, Ap- atosanrus, and Camarasaurus. Inferior border Etymology. — Supersaurus , internationally of scapula forming a gentle curve from glenoid published vernacular name; vivianae, after Vi- process to distal end, resembling Apatosaunis vian Jones, co-discoverer of all the important and Diplodociis rather than Brachiosaunis or Late Jurassic fossil localities on the Uncompah- Camarasaurus. Inferior fossa not broadly ex- gre Upwarp. panded as in Brachiosanrus and longer than 5500, scapulocoracoid HOLOTYPE. —BYU wide, contrasting with opposite design in Ap- 2.44 m (8') long. atosaurus and Camarasaurus . Coracoid with a Referred material. —BYU 5501, scapuloco- subrectangular profile. racoid 2.70 m (8,10") long; BYU 5502, ischium; Referred material. — BYU 5501, scapu- BYU 5503, medial caudal vertebra; BYU 5504, locoracoid 2.70m (8' 10") long. Description vertebrae. 12 articulated caudal same as Holotype, BYU 5500. Type locality. — Drv Mesa quarry; E 1/2, BYU 5502, 12 articulated caudal vertebrae: Section 23: T50N, R 14W, NMPM. each approximately 30 cm long, collected but Horizon. — Near the base of the Brushy Basin not yet prepared for study. They were exam- Member of the Upper Jurassic Morrison Forma- ined closely in the field by the author, and a tion, Mesa County, Colorado. decision was made to refer them to Supersau- Collector. —James A. Jensen 1979. rus on the basis of their massive size and Clarification. — Sauropod scapular termi- general morphology. They were found paral- scapula; how- nology in the literature is not uniform (Hatcher lel to, and near the Supersaurus 1903, Mook 1921, Gilmore 1936), resulting in ever, location is not a criterion for association some confusion. This paper describes the in the Dry Mesa cjuarry because of the exten- to scapula in a somewhat normal orientation; using sive fluvial transport of all elements prior an external view with the glenoid cavity down final burial. and the coracoid on the right end, the right BYU 5503, ischium (Fig. 7A): straight shaft, ex- scapula will be described. Descriptive terminol- more robust than Diplodocus; distal end ventrally. Very ogy used: narrow midsection is the "shaft"; left panded dorsally, truncated end is the "distal" end; upper edge is the similar to Diplodocus "superior border"; lower edge is the "inferior BYU 5504, two medial caudal vertebrae border"; ventral projection of glenoid area is the (Figs. 7C, D, Dl). C, double-keeled, diplo- 702 Great Basin Naturalist Vol. 45, No. 4 October 1985 JENSEN: New Sauropod Dinosau ,5 m , 704 Great Basin Naturalist Vol. 45, No. 4 coid caudal with broad ventral channel; D, preparation by the author) appears to be al- Dl, double-keeled diplocoid caudal with tithorax (see Figs. lA, B; 3A-D). transveisely thick neural spine that is ex- Figure 3C is a detail of the base of the panded dorsoventrally at its summit. The cau- neural spine and postzygapophyses of BYU dal neural spines oi Diplodociis are thin, nar- 5000. The form of the suprapostzygapophysal row, and unexpanded at the summit; caudal laminae is greatly altered by assymetry, with rib missing, no pleurocoel but a short channel the right side being more robust than the left. exists below base of caudal rib. Proportion of The vertebra is crushed transversely, making diameter-to-length would place the specimen an anterior view nearly useless. The neural as number 12 in a Diplodociis caudal series, spine is tall and buttressed posteriorly by but the reduction of the neural arch would suprapostzygapophysal laminae 2/3 the height place it much further back in the same series. of the spine (Fig. 3B). In contrast, the supraprezygapophysal laminae are almost Order Saurischia nonexistent.