Great Basin Naturalist Volume 47 Number 4 Article 9 10-31-1987 New brachiosaur material from the Late Jurassic of Utah and Colorado James A. Jensen Provo, Utah Follow this and additional works at: https://scholarsarchive.byu.edu/gbn Recommended Citation Jensen, James A. (1987) "New brachiosaur material from the Late Jurassic of Utah and Colorado," Great Basin Naturalist: Vol. 47 : No. 4 , Article 9. Available at: https://scholarsarchive.byu.edu/gbn/vol47/iss4/9 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]. NEW BRACHIOSAUR MATERIAL FROM THE LATE JURASSIC OF UTAH AND COLORADO James A. Jensen' Abstract —Little is known about the Brachiosauridae, which includes some of the largest known sauropods, such as the genus Brachiosaurus, discovered in western Colorado by Elmer S. Riggs in 1900. Additional diagnostic material, previously unknown in the western hemisphere, is reported from three comparatively recent quarries: the Jensen/ Jensen Quarry in eastern Utah and the Dry Mesa and Potter Creek quarries on the Uncompahgre Upwarp in western Colorado. An unknown, well-preserved, articulated sauropod atlas/axis, seven cervical vertebrae, and an interesting flora were associated with the Potter Creek Quarry brachiosaur material. Taphonomic factors in that quarry are noted. The Jensen/Jensen and Dry Mesa deposits occur in basal sediments of the Brushy Basin Member of the Morrison Formation, and the Potter Creek Quarry in an intermediate section of that member. No complete, articulated skeleton of the A decade later a second discovery of bra- sauropod genus Brachiosaurus has been re- chiosaur bones was collected by a German ported from North America. However, an in- paleontologist, Janensch, in Tendaguru, Tan- complete skeleton was collected in Colorado zania, formerly East Africa. He recovered a in 1901, and disarticulated bones of the genus fairly complete skeleton that he named B. have been found in at least four other locali- brancai (Janensch 1914); the restored skele- ties. Elements described here, not previously ton is now mounted in the Museum fiir reported from the western hemisphere, in- Naturkunde in East Berlin, East Germany. clude a partial scapula, a distal cervical verte- Subsequent work by British expeditions, and bra, a radius, a metacarpal, and a humerus. possibly other European institutions, recov- The radius, metacarpal, and humerus appear ered other brachiosaur materials from Tanza- to represent a novel species but will not be nia, but for more than 80 years no additional described here as such. brachiosaur remains were scientifically re- In 1900 the type-species of the genus Bra- ported from the western hemisphere. chiosaurus was collected by Elmer S. Riggs, Circa 1943 a brachiosaur skeleton in an ad- of the Field Columbian Museum, Chicago, vanced state of erosion was discovered on the who discovered a partial skeleton of this re- Uncompahgre Upwarp in western Colorado markable sauropod near Grand Junction, Col- by the late Daniel E. Jones and his wife, Vi- orado. This skeleton possessed the previously vian, of Delta, Colorado. The humerus (Figs. unknown feature of front legs equal in length 2B, 3A-D, 4B) was collected and donated to to the rear (Fig. 1), which elevated the base of the U.S. National Museum in Washington, the neck and thorax far above any spinal incli- D.C., but was never described. The discov- nation previously reported in sauropods. ery site, approximately 70 km SSE of the Riggs (1903) appropriately named it Bra- Riggs locality, was named the Potter Creek chiosaurus altithorax. He recovered approxi- Quarry. Its stratigraphic position is approxi- mately 20 bones, including seven articulated mately in the middle of the Brushy Basin presacral and two caudal vertebrae, a sacrum Member of the Morrison Formation. I and the right ilium, a left coracoid, right worked there two seasons (1971, 1975), col- humerus, right femur (Fig. 1), and four ribs. lecting five disarticulated elements of a large The femur and humerus were greatly com- sauropod (? B. altithorax), bones of a second, pressed, with the distal end of the latter being smaller sauropod genus, and teeth of an un- partially destroyed by surface erosion (Fig. 1). known theropod. The brachiosaur elements This material is now preserved in the Field collected include part of the discovery Museum of Natural History, Chicago. humerus (Figs. 3E, 5A-D, 6B), a medial '2821 North 700 East, Provo, Utah 84604. 592 JENSEN; New Dinosaur Material 593 Bi C Fig. 1. A-D, F-H, elements of the type o( Brachiosaurns altithorax (from Riggs 1904): A, humerus, anterior view; proximal Ai, end; B, femur, anterior view; Bi, proximal end view; C, right ilium; D, fifth presacral vertebra; E, Potter Creek Quarry brachiosaur, fourth or fifth presacral vertebra; F, thoracic rib head, anterior view; G, B. altithorax, thoracic rib head, mesio-anterior view; H, B. altithorax. lateral view of left coracoid. Scale: A-D, F-H, approximately 1/12 natural size. dorsal vertebra (Figs. 3D, 4A-A3), an incom- vertebral series from the atlas/axis to the sev- plete left ilium (Fig. SA-A^), and a left radius enth cervical vertebra. This series was found and metacarpal (Figs. 3B, 5E-Ei). Materials intact but excavated in fragments by the Jones of the smaller, indeterminate sauropod in- family and given to me. I was able to reassem- clude the broken fragments of an articulated ble an articulated atlas/axis and third cervical 594 Great Basin Naturalist Vol. 47, No. 4 i^ i^»fe iiT * Mm Fig. 2. A, Jensen/Jensen Quarry: scapula with coracoid in foreground (the only existing illustration of these unprepared brachiosaur elements); worker in upper right corner is sawing around border of 9' brachiosaur rib; B, Potter Creek Quarry. vertebra (Fig. lOA-E) from this broken mate- elements noted here are much too short and rial because of its excellent preservation. A small for any described brachiosaurid. detailed study of some of this material is in In 1960 I discovered a dinosaur bone de- progress, but a preliminary examination re- posit in basal Brushy Basin Member sedi- veals it to be from a mature sauropod. The ments of the Morrison Formation near October 1987 JENSEN: New Dinosaur Material 595 Fig. 3. Potter Creek Quarry brachiosaur: A-A2, left ilium (dorsal border, ischiadic peduncle restored); B, radius; C, metacarpal; D, fourth or fifth dorsal vertebra; E, left humerus. Abbreviations: dc, deltoid crest; ms, muscle fossa. Jensen, Utah. This deposit (the Jensen/Jensen with the scapula does not appear to match the Quarry) is located south of the Green River, a coracoid of B. altithorax, the specific identity few miles from the Dinosaur National Monu- of the elements is presently in question. ment Quarry. Two years' work (1962, 1966) in When fully prepared, the material may repre- this quarry (Figs. 11, 13) produced several sent an undescribed species; but an in- brachiosaur elements including a rib 2. 75 m (9 sufficient number of elements duplicating ft) long (Fig. 6B), a distal cervical vertebra, those of the type-species presently precludes the proximal half of a scapula, and a coracoid. such a determination. Additional, well- Many worthless slivers and fragments of shat- preserved brachiosaur material, cited in the tered brachiosaur cervical vertebrae were en- Uncompahgre fauna (Jensen 1985), is de- countered. Because the coracoid associated scribed here from the Potter Creek Quarry. 596 Great Basin Naturalist Vol. 47, No. 4 Fig. 4. Dorsal vertebrae: A-A3, Potter Creek Quarry brachiosaur, fourth or fifth dorsal vertebra, right lateral view; B-B2, Dystijlosaurus edivini, type (B), anterior (B,), posterior (B,), right lateral views, probably anterior dorsal; C, Ultrasaurus macintoshi, type posterior dorsal vertebra, 1.45 m tall, lett lateral view. October 1987 JENSEN; New Dinosaur Material 597 Fig. Potter 5. Creek Quarry: A-D, brachiosaur humerus. A, proximal end; B, mid-shaft section; C, detail of bulbous deltoid crest; D, anterior, distal end; E, metacarpal MC I, mesial view; Ej, same, lateral view. Abbreviations: dr, deltoid ridge; ms, muscle fossa/scar. 598 Great Basin Naturalist Vol. 47, No. 4 Fig. 6. A, Scapulocoracoid referred to Ultra.saunis nuicintoshi. prone figure 6'.3" tall; B, Jensen/Jensen Quarry brachiosaur rib, Dry Mesa Quarry Ultrasaunts scapulocoracoid. Potter Creek Quarry brachiosaur left humerus. All three elements cast in fiberglass resin. October 1987 JENSEN: New Dinosaur Material 599 y?fiL:^dl^ J I m Fig. 7A-B. Reconstructed front limb with cast scapulocoracoid of Ultrasaurus macintoshi (figure 6'3" tall): A, mid-cervical vertebra, Supersaurus vivianae, anterior view (original seen in Fig. 8); B, same, left lateral view. Vertebra restored from original and cast in fiberglass resin. This material is much better preserved than nosis (see Systematic Paleontology). that of the type of B. altithorax (Riggs 1903) In 1972 I opened a quarry near Dry Mesa and justifies some revision of the generic diag- (Dry Mesa Quarry) in basal Brushy Basin 600 Great Basin Naturalist Vol. 47, No. 4 poc Fig. 8. A, Proximal end of brachiosaur femur, proximal end 5'6" in circumference, from Recapture Member of the Morrison Formation; B, Siipersatirus vivianae, right lateral view of mid-cervical vertebra; C, mid-cervical vertebra, Supersaurus vivianae right lateral view (restoration seen in Fig. 7). Abbreviations: acx, anterior convexity; bns, bifurcate neural spine; idl, infradiagonal lamina; poc, posterior concavity; pp, parapophysis; prdl, prediapophysial lamina; prz, prezygapophysis; pz, postzygapophysis; sdl, supradiagonal lamina; tp, transverse process; vl, ventral lamina. Member sediments on the NE monocline of related materials including bones of several the Uncompahgre Upwarp in western Colo- unusually large sauropods (Jensen 1985), rado.