Volumina Jurassica, 2014, XII (2): 197–210DOI: 10.5604/17313708 .1130144 Haplocanthosaurus (Saurischia: Sauropoda) from the lower Morrison Formation (Upper Jurassic) near Snowmass, Colorado John R. FosteR1, Mathew J. Wedel2 Key words: Haplocanthosaurus, sauropod, Late Jurassic, Morrison Formation. Abstract. A small sauropod dinosaur collected from the Rocky Mountains of central Colorado (north of the Elk Range, Pitkin County) is assigned to the rare genus Haplocanthosaurus. The specimen, MWC 8028, consists of four dorsal centra, five partial ribs, the sacrum, five caudal vertebrae, three chevrons, five partial neural spines and many fragments and is from the lower third of the Upper Jurassic Morrison Formation. The dorsal vertebrae are procamerate, and on the sacral vertebrae the neural arch peduncles are vertically elongate and the neural spines are strongly reclined. The only sauropod from the Morrison Formation that shares these characters is Haplocanthosaurus and based on those characters MWC 8028 is referred to Haplocanthosaurus. This is at most the tenth specimen and the seventh locality for this sauropod, all within the Morrison Formation. INTRODUCTION Haplocanthosaurus is one of the rarest sauropods of the Upper Jurassic Morrison Formation of the western United States. This sauropod was first described as Haplocanthus from specimens collected at the Marsh-Felch Quarry at Garden Park, Fremont County, Colorado, around the turn of the last century (Hatcher, 1903a). Hatcher (1903b) revised the name to Haplocanthosaurus several months later because he mistakenly believed Haplocanthus was preoccupied. Haplo canthus was technically correct until a 1991 ICZN ruling (ICZN, 1991) that established Haplocanthosaurus as the correct name due to widespread use, based on a proposal by Lucas and Hunt (1989). Hatcher (1903c) provided a detailed description of the osteology of Haplocanthosaurus based on the Marsh-Felch Quarry specimens. CM 572, the genus holo type, was named as H. priscus, and CM 879, also from the Marsh-Felch Quarry, was designated the holotype of the spe- cies H. utterbacki, although this latter specimen has generally been regarded as a juvenile and a subjective synonym of H. priscus (McIntosh, 1990a; Upchurch et al., 2004). McIntosh and Williams (1988) named H. delfsi on the basis of a partial skeleton about 50% larger than the H. priscus type material. Haplocanthosaurus delfsi was also found in the Garden Park area but in the Cleveland Museum Quarry south of the Marsh-Felch Quarry. Whereas common sauropods from the Morrison Formation such as Camarasaurus, Diplodocus, and Apatosaurus (Dodson et al., 1980) are known from specimens representing minimum numbers of individuals (MNI) ranging from approximately 100 to more than 170 (Foster, 2001, 2003), Haplocanthosaurus is known from fewer than a dozen (and possibly as few as four) specimens, most represented by a handful of elements. By far the best preserved and most complete specimen of a haplocanthosaurid, FHPR 1106, was excavated from west of Dinosaur National Monument in 1 Museum of Moab, 118 East Center St., Moab, UT 84532 USA; email:
[email protected] 2 College of Osteopathic Medicine of the Pacific and College of Podiatric Medicine, Western University of Health Sciences, 309 East 2nd St., Pomona, CA 91766, USA Ohio. the Morrison is approximately 90 m thick (Mutschler. Jensen. 2C). Freeman. Colorado (Figs 1. Fruita. FHPR – Utah Field House of Natural History Museum. To the south is the Elk Range. Gordon-Bramson-Brothers Quarry locality map Thick line indicates outcrops of the Morrison Formation. Locally. Triebold Paleontology had previously worked the site briefly and determined that the material belonged to a sauropod but was not interested in working the site further. Chicago. 1972). 1970. Pittsburgh. and overlying the Morrison is the Burro Canyon Formation (Mutschler. CMNH – Cleveland Museum of Natural History. This stratigraphic level. Colorado. downstream on Snowmass Creek. 1999). The strata are south-dipping (~35°). Underlying the Morrison here are the Entrada Sandstone and the Curtis Formation. SMM – Science Museum of Minnesota. then a college student exploring his grandfather’s land. 1970. quarry indicated by star . in a cut through a hogback made by Snowmass Creek in Pitkin County. The town of Snowmass is approximately 1. Excavations continued at the site each summer through 2013. 1972). Utah.6 km north of the quarry. Wedel 198 1999. and the exposed formations range from Permian and Triassic through Late Cretaceous (Mancos Shale). Foster. approximately 27% of the way up into the local Morrison section. GEOLOGICAL SETTING The present specimen was found by Mike Gordon. Utah. Paul. Peterson. The Museum of Western Colorado collected the exposed bones and others in one jacket from July–September 2009. ABBREVIATIONS CM – Carnegie Museum of Natural History. Any occurrences of these rare and relatively small sauropods are of interest. DINO – Dinosaur National Monument. 1. Gordon’s mother. although the lithology of the site Fig. Jessica Bramson.John R. 2B). The quarry is approximately 24. Illinois. Vernal.5 m above the base of the Morrison Formation (Fig. Cleveland. In 2009. Mathew J. contacted the Museum of Western Colorado and its crews investigated the site that June. The Gordon-Bramson-Brothers Quarry is in the lower Morrison Formation. MWC – Museum of Western Colorado. is approximately equivalent to the middle Salt Wash Member of the Colorado Plateau (Turner. Freeman. FMNH – Field Museum of Natural History. St. especially given their apparent restriction to the lower half or so of the Morrison Formation. Minnesota. View looking north . Gordon-Bramson-Brothers Quarry A. 2. B. Stratigraphic section showing position of the quarry within the Morrison Formation. C. Dragging field jacket containing the sacrum.Haplocanthosaurus (Saurischia: Sauropoda) from the lower Morrison Formation (Upper Jurassic) near Snowmass. one caudal. and two dorsal centra in September 2009. Quarry map showing association of anterior caudal and posterior dorsal vertebrae around the sacrum. Colorado 199 Fig. overlying a soft red mudstone. associated partial skeleton (Fig. 3–7 Referred Specimen. – The dorsal centra are thick-walled with procamerate pneumatic chambers (Fig. caudal 195 – ~95 – . their Table 1 Measurements of vertebrae in MWC 8028. 1903 Haplocanthosaurus sp. five caudal vertebrae. the ventral half of the centrum is solid in each vertebra. D). Wedel 200 more closely matches the mudstone-limestone interbedding common in lower Morrison Formation outcrops of the Front Range area of Colorado. Description. This stratigraphic level also puts the site at the approximate equivalent level (compared to respective local sections) as the Cabin Creek site near Gunnison (Bartleson. – MWC 8028. 3B. Williams. see Table 1). the latter of which produced Haplocantho saurus delfsi (McIntosh. Vertebra Centrum height [mm] Centrum width [mm] Antero-posterior length [mm] Total height (centrum and neural spine) [mm] Dorsal A 150 100 130 – Dorsal B 160 110 105 – Dorsal C – – ~100 – Dorsal D – 85 110 – Sacral 1 or 2 – – – 600 Sacral 4 or 5 165 ~120 – 545 Caudal 1(?) 197 – 82 – Caudal 2(?) 178 ~150 60 420 Caudal 3 or 4(?) 157 148 84 – Caudal 4 or 5(?) 155 – 90 – Indet. The Gordon-Bramson-Brothers Quarry is in a gray-green indurated mudstone and light gray siltstone. 1988). 2A). Foster.John R. most likely by Pleistocene frost-wedging at the site elevation of about 2. and the lateral pneumatic fossae are anteroposteriorly elongated but shallow ventrally (Fig. 1986 Haplocanthosaurus Hatcher. also noted by Mutschler (1970) elsewhere in the area in the lower Morrison Formation. Haplocanthosaurus sp. Many of the pre-existing cracks in the specimen had matrix between them. from the base of the Morrison Formation up to within a few meters of the quarry stratigraphically. Mathew J. the sacrum. and reassembly of the specimen was particularly challenging. A lthough the dorsal elements are not complete. The specimen is highly fractured. 3A–F). The sauropod specimen described herein is an isolated and disarticulated. the specimen is judged to represent a single individual because there are no duplicated elements nor are there any other dinosaur species in the deposit. Below the quarry. is an interval of interbedded gray mudstone and limestone beds. five partial neural spines and many fragments. 1842 Saurischia Seeley. SYSTEMATIC PALEONTOLOGY Dinosauria Owen.164 m and by root-wedging of a scrub-oak that was growing in the mudstone just above the specimen. 1888 Sauropodomorpha Huene. three chevrons. Figs. including two of the caudal vertebrae. Specimens deeper (down dip) in the quarry. with a thin medial septum. 1878 Neosauropoda Bonaparte. Jensen. The dorsal centra are small (~15–16 cm diameter. Although the site is not yet fully excavated. 1932 Sauropoda Marsh. 1988) and the Cleveland Museum’s Delfs Quarry at Garden Park. fragmentary partial skeleton consisting of four dorsal centra. were in somewhat better condition but were still fractured. five partial ribs. in the three best preserved vertebrae the lower borders of the lateral pneumatic fossae are preserved but the top of the centrum and all of the neural arch is missing. C. MWC 8028. Dorsal view of same centrum as in A. B. F.Haplocanthosaurus (Saurischia: Sauropoda) from the lower Morrison Formation (Upper Jurassic) near Snowmass. Haplocanthosaurus dorsal vertebrae A. Lateral view of dorsal centrum with bottom edge of lateral pneumatic fossa preserved. 3. Colorado 201 Fig. again showing the median septum and paired lateral fossae. Dorsal neural spines in lateral (top) and anterior or posterior (center. Lateral view of dorsal centrum with partial pleurocoel preserved. Lateral view of dorsal centrum with smaller segment of the lateral pneumatic fossa margin preserved. showing the median septum between the paired lateral fossae. E. G. Cross-sectional (posterior) view of same dorsal as in E. Dorsal view of same centrum as in C. bottom) views. D. Scale bars = 10 cm . 3G) are non-bifurcate but differ from those intact on the anterior caudals in being slightly laterally expanded. and have rectangular crosssections with relatively flat ventral surfaces and straight . MWC 8028.202 John R. and a nearly circular dorsolateral fossa above the sacral rib attachment. The centra are only ~15–20 cm in diameter and moderately amphicoelous to slightly procoelous (the differences between vertebrae likely preservational). after Hatcher (1903c: plate 4). sacrum in right lateral view with divisions between the vertebrae overlaid. Additionally. but the latter is reconstructed between the spines and centra. which we take to be S4 and S5. Mathew J. C. B–E are not shown at the same scale. The spine to centrum diameter ratio is lower than that seen in Diplodocus. MWC 8028 with divisions between the vertebrae overlaid. the height to centrum diameter ratio of MWC 8028 is comparable to CM 879 (Fig. sacrum in right lateral view. 4A–C) consists of at least five fused vertebrae with centrum diameters of approximately 16 cm. Note that the neural arches in CM 572 were restored during preparation. 4C. E. close-up of S4 and S5 centra highlighting pneumatic fossae. and the sacral neural spines as shown here are probably lower than they would have been in life a ssociation with the sacrum suggests that they are posterior dorsal centra. large lateral fossa. Wedel Fig. The anterior caudal vertebrae (Fig. 4. D) but higher than it appears to be in CM 572 (Fig. The sacral neural arches are relatively tall. The sacral neural spines are graded from a nearly vertical orientation in S1 to strongly posteriorly inclined in S4. CM 572 in right lateral view. so the true arch height is difficult to assess in that specimen). B. The sacrum (Fig. S4 has a small lateral fossa below the attachment of the sacral rib (which is broken away). S5 bears only a single. Sacra of Haplocanthosaurus A. CM 879. the spine of S5 was not preserved. D. Pneumatic fossae are present in the last two sacral centra. MWC 8028. but this may be in part due to lateral compression. The dorsal neural spines (Fig. 4E. They are antero-posteriorly short for their diameters. scale bar for A = 20 cm. 5A–K) are small with closed neurocentral sutures and no lateral pneumatic fossae. Foster. Caudal 2(?). E. Chevron in posterodorsal view. 5. I. H. MWC 8028. C. close-up of neural canal in posterior view with the ventral excavation highlighted by the arrow. Scale bars = 10 cm . Haplocanthosaurus. Caudal 3 or 4 in anterior view. Caudal 1(?) in posterior view. G. Caudal 2(?) in posterior view. caudal elements A. Caudal 4 or 5 in anterior view. close-up of neural canal in posterior view with the ventral excavation highlighted by the arrow. F. Caudal 2(?) in anterior view. Caudal 1(?). J. Caudal 4 or 5 in posterior view. L. D. K.Haplocanthosaurus (Saurischia: Sauropoda) from the lower Morrison Formation (Upper Jurassic) near Snowmass. Caudal 2(?) in left lateral view. Colorado 203 Fig. B. Caudal 1(?) in right lateral view. Caudal 1(?) in anterior view. Fragments of posterior ribs. 6. ribs A. 17). 1921: fig. Mook. C. Cross-section of Diplodocus torso at the seventh dorsal vertebra (after Holland. Mathew J. with the rib from B overlaid. Haplocanthosaurus. Scale bar = 20 cm . MWC 8028. D. 72). B. Cross-section of Camarasaurus torso at the fourth dorsal vertebra (after Osborn.204 John R. the three pieces shown here do not belong to the same rib. with the rib from B overlaid. 1910: fig. Foster. The most complete posterior rib. Wedel Fig. B) with the most complete being a short posterior rib that is approximately 1 m in length along its lateral edge. MWC 2538 preserves in the dorsal vertebrae transversely expanded rugose neural spines. Apatosaurus. narrow torso like most other non-titanosaurian sauropods (Fig. and the spines of MWC 8028 are a bit more reclined still. The dorsal neural spines of MWC 8028 are expanded only slightly and nowhere near their development in Camarasaurus. and shows the least change in angle of the sacral neural spines along the series. and second. even in juvenile specimens (pers. Ontogenetic patterns of ossification in the sacral vertebrae of Morrison Fm. We note that CM 879 is least skeletally mature of the three specimens discussed here. The only other Morrison Formation sauropods with posterior sacral neural spines that are reclined to a similar degree as MWC 8028 are Brachiosaurus altithorax (see Riggs. and the stratigraphic level of its occurrence is consistent with the likelihood that the material belongs to this species. Even very young juvenile brachiosaurids appear to have had these relatively elongate dorsal centra (Carballido et al. The ribs are very incomplete (Fig. The excavations in the neural canals of the caudal vertebrae of MWC 8028 are absent in CM 572 and FHPR 1106. 7A–B). 6C. 5D. and. can it be referred to any of the known Morrison Formation sauropods? The only characters in MWC 8028 that stand out as possibly being unique are the extremely reclined spines of the posterior sacral vertebrae. and there are indications of anterior facets as well. (2007) presented evidence for supramedullary pneumatic diverticula inside the neural canals of sauropods. 7C. so that the three specimens form a sort of grade or cline. lack laminae. and in all other Morrison Formation sauropods that we have examined. D). The chevron facets are large. which are generally camerate to polycamerate (Wedel. CT scans of two posterior dorsal centra of a juvenile Camarasaurus grandis (MWC 2538) from the Morrison Formation at the Kings View Quarry near Fruita. Brachiosaurus possesses much shorter sacral neural spines than MWC 8028 and has significantly more anteroposteriorly elongate dorsal centra (relative to their diameters). The ribs are all apneumatic but otherwise mostly uninformative. and the floor of the neural canal is depressed a few millimeters into the dorsal surface of the centrum (Fig. Postcranial pneumatic features are notoriously variable (Wedel. Given that MWC 8028 lacks robust autapomorphies. E). 2009). and the unusual excavations in the neural canals of the caudal vertebrae.. and even the anterior caudal neural spines are somewhat laterally expanded. similar to those found in extant birds. in cross-sectional CT views of the dorsal centra.).. priscus. 2003). For these reasons. it seems unwise to attach any taxonomic weight to this character. MWC 8028 is procamerate. obs. elongate neural spines with multiple laminae. Various morphological aspects prevent definitive identification of the material as any of the common diplodocid sauropods of the Morrison Formation (Diplodocus. Barosaurus). similar excavations have been noted in other. although they do show that the animal had a deep. Colorado. and the sacral and anterior caudal neural spines are not expanded at all. Welldefined pneumatic fossae on the centra of the sacral vertebrae are absent in Camarasaurus (Wedel.Haplocanthosaurus (Saurischia: Sauropoda) from the lower Morrison Formation (Upper Jurassic) near Snowmass. the question arises of whether it is referable to a known taxon. 1904: plate 73) and Haplocanthosaurus priscus (Fig. D). 1979). 2012). 4D. Camarasaurus possesses laterally expanded. unlike Camarasaurus. show that even in young individuals of these sauropods the dorsal centra are strongly pneumatic and camerate (Fig. The caudal ribs are simple and fused to the centra. it is reasonable to expect that it will also be variable. and caudal pneumaticity is present in CM 879. This character seems to be subject to individual variation – the posterior sacral neural spines in CM 572 are more reclined than in CM 879. 4B). fan-like dorsal neural spines. 2013: table 1). MWC 8028 lacks the wing-like caudal ribs.6 cm in diameter. The neural spines are simple. unlike even juvenile macronarians and diplodocids in the Morrison Formation. and to the extent that “fanning” of the sacral neural spines is related to fusion of the sacral neural arches and spines. diplodocids. their presence is likely due to individual variation. 1903. Preserved chevrons (Fig. Schwarz et al. and the centra are approximately 14. 6A. 2005). IDENTIFICATION In identifying MWC 8028 we asked two questions: first. does the specimen bear any unique characters that might establish it as a new taxon. and fully camerate or polycamerate centra seen in Morrison Fm. However. Wedel. but present in MWC 8028 (Fig. . with nearly all of the lower half of the centrum consisting of solid bone (Fig. relatively less derived sauropods such as Barapasau 205 rus (Jain et al. sauropods are highly variable (Riggs. The neural canals are unusual: the anterior opening of each canal is smaller and set higher (more dorsally) than the posterior opening. not fused proximally and unexpanded distally. and are unexpanded dorsally. MWC 8028 is most similar in size and vertebral morphology to Haplocanthosaurus priscus (CM 572). H). Whether the excavations in the neural canals of the caudal vertebrae in MWC 8028 are pneumatic or not. if the specimen does not represent a new taxon. Taylor. has a low degree of pneumaticity. It is possible that the excavations are pneumatic in origin – fossae on the sacral vertebrae of MWC 8028 show that pneumatic diverticula extended at least that far caudally. unfused neurocentral sutures. 5L) are simple. Colorado lateral sides. like H. In both specimens. 2003. fig. the procamerate dorsal centra are of taxonomic significance and strongly suggest that the material belongs to Haplocantho saurus. the fourth sacral vertebra has a circular dorsolateral fossa just above the attachment of the sacral rib. fig. the only procamerate sauropod in the Morrison Formation (Wedel. 2003). Mathew J. In MWC . The sacral pneumatization in MWC 8028 is very similar to that present in the CM 879 specimen of Haplocanthosau rus priscus. Foster. In C and D. In CM 879 a lateral fossa is present on the right side of S4 but absent on the left side of S4 and also absent on both sides of S5. as in MWC 8028 (Wedel. Dorsal centum diameters in all four vertebrae are approximately 15–16 cm. 8. the ventral half of each dorsal centrum is solid. of a size comparable to those of MWC 8028. 2009. and in fact nothing in the skeleton suggests a young individual.206 John R. lower halves of the centra are solid and fossae are shallow. 7. 6) That dorsal centra of positively identifiable juvenile Camar asaurus. already demonstrate dramatically more pneumaticity indicates that MWC 8028 is unlikely to be simply a young individual of a more camerate sauropod species. In CM 572 (H. The simple fossae of MWC 8028 are not a result of young age. Note procamerate condition of centra in A and B. priscus). rather. C and D) Interpretive outlines of bone in each centrum below the CT scans. These images contrast the much more pneumatic condition of the dorsal centra of even a juvenile Camarasaurus (C and D) with the more solid construction of the centra of MWC 8028. Lateral fossae are more variable. Wedel Fig. Wedel. the centra are camerate and the arrows point to the contact between the lower and upper edges of the camerae and the infilling matrix. CT scan image cross-sections of dorsal vertebral centra in MWC 8028 (referred to Haplocanthosaurus. A and B) and in a juvenile Camarasaurus grandis (MWC 2538. 1990a. b) or. most often.13 times the centrum height. Nor does it appear to be a new taxon. characters of the limb elements are not among the autapomorphies listed for Haplocanthosaurus by Wilson (2002) or Whitlock (2011). In summary.. 2003. lateral fossae are present on the right side of the centrum in both S4 and S5. 2014) in Wyoming. Colorado). DISTRIBUTION Haplocanthosaurus is rare in the Morrison Formation. CLASSIFICATION Haplocanthosaurus has had a bit of an unstable systematic history. Regarding the SMM specimen from Poison Creek. to be a diplodocid (K. pers. 1995.Haplocanthosaurus (Saurischia: Sauropoda) from the lower Morrison Formation (Upper Jurassic) near Snowmass. Bones from the Gordon-Bramson-Brothers Quarry add little to the character list for Haplocanthosaurus. 2012). fig. For example. although others have had it either in the Cetiosauridae (McIntosh. The height of the sacral neural spines in CM 572 may be an underestimation. characteristic on which to identify material. 2000). comm. 1988). 2014). isolated bones that may belong to Haplocanthosaurus include the Red Fork of the Powder River Quarry B in Wyoming (McIntosh. and the sacral and caudal vertebrae are ~50% smaller than CMNH 10380 (H. FHPR 1106 (haplocanthosaurid). 1998. Pisani et al. to this genus from the Red Fork of the Powder River B. and the Carnegie Quarry (Dinosaur National Monument catalog. That MWC 8028 has a higher ratio than FHPR 1106 may in part be due to lateral crushing of the former specimen. and compiled in Sander et al.. Other sites with unconfirmed. and because the specimens previously identified as belonging. both Garden Park. or possibly belonging. It has been classified as a macronarian close to Camarasaurus and Brachiosaurus (Upchurch. The specimen from Freezeout Hills Quarry N (listed by Foster. and the Gordon-Bramson-Brothers Quarry is just the fourth locality to produce more than isolated elements attributed to this sauropod. but the specimen is still under study and the generic identification has not been released (Bilbey et al. pers. 1998. Whitlock. Williams. Therefore we refer MWC 8028 to Haplocanthosaurus sp. Cleveland Delfs. and Carnegie Quarry are based on either caudals or girdle and/or limb material. Colorado 8028. Perhaps the most interesting part of the skeleton preserved is the sacrum. In some cases it has been hypothesized as a basal neosauropod outside both Diplodocoidea and Macronaria (Harris. and the Poison Creek Quarry (Erickson. because the bases of the spines. delfsi. It is therefore possible that confirmed Haplocanthosaurus specimens are known only from the Marsh-Felch. the posterior sweep of the sacral neural spines in MWC 8028 is not entirely unexpected. 2003 based on a single caudal from the FMNH) is one we cannot relocate or confirm.. Wilson. Carpenter. which demonstrates relatively higher spined and slightly more posteriorly inclined sacral neural spines than previous specimens such as CM 572 and FHPR 1106. for comparison. 2006. and Gordon-Bramson-Brothers quarries and include just four individuals. particularly S4. the scapula from the Carnegie Quarry (DINO 4771. 2011.. appear to be heavily reconstructed. The full height of sacral 5 in CM 572 is approximately 2. The nearly rectangular cross-section of the anterior caudal vertebrae in MWC 8028 (relatively straight sides and ventral surface) is similar to what is seen in CM 572 and FHPR 1106. in Diplodocus (CM 94). but only slightly smaller than. and thus subjective. 2002. the same ratio in FHPR 1106 is 2. 1988) and MarshFelch Quarry (Hatcher. 1903c. D. Naish.95. Wilson. McIntosh. the full height is 3.. Sereno. 2002. on removal of more material. Upchurch et al. 2014). sauropod. MWC 8028 has a full sacral height to centrum height ratio of 2. The Garden Park Sauropod Quarry specimen reported in Carpenter (1998) and Foster (2003) proved. Poison Creek. Williams. we consider these identifications tenuous. Mannion et al. the enlarged chevron facets of Haplocanthosaurus can be distinctive in concert with other characters but are a somewhat variable.44 times the height of its centrum. 1986b. Evanoff. The Williams Slow Eagle Quarry in Utah produced the most complete and well-preserved specimen of a haplocanthosaurid. Table 2) lacks the dorsally and ventrally expanded distal shaft listed as an autapomorphy of Haplocanthosaurus by Wilson (2002) and may instead belong to Camarasaurus. 2011.. we suspect this is a misidentification. 207 comm. but sacra of this and other specimens suggest that the sacral neural spines are not as low as previously thought. as FHPR 1106 demonstrates this characteristic to a somewhat lesser degree also. See Table 2 for a summary of specimens. MWC 8028 is similar in morphology. however. The previous sites include: the Cleveland Museum Delfs Quarry (McIntosh. MWC 8028 share several characters with Hap locanthosaurus. 1981). 2005). 4). Foster. But. often residing near the Macronaria-Diplodoco idea split (Taylor. but does not closely resemble any other known Morrison Fm.. We note that the most diagnostic elements of Haplo canthosaurus are the dorsal vertebrae. allied with the Diplodocoidea as a basal taxon (Bonaparte. 2004). Chure. Carpenter. .80. . left tibia. fragmentary coracoids. pers. left ulna. 19 caudals. scapular. fibula. seven ribs. 13 dorsals. ribs. Foster. femur Ten cervicals. DNM Poison Creek Wyoming Colorado Gordon-BramsonBrothers Poison Creek Colorado Colorado Colorado State Cleveland Delfs Marsh-Felch Marsh-Felch Quarry See text for additional details regarding some identifications CMNH 10380 CM 879 H. partial radius and 1988 ulna. astragalus. pubes.15. three chevrons Four cervicals. left ilium. sacrum. Foster. 2003 DNM catalog. calcanea. astragali. 1981 This paper Five cervicals. pubes. ischia. parMcIntosh and Williams. probably also includes CM 33995 (scapHatcher. sacrum. ilia. sternal plate. sacrum. Wedel . 14 caudals. calcaneum. 10 metacarpals. 37 caudals. 19 chevrons. right scapula. delfsi CM 572 Specimen Number H. DNM Utah Utah Carnegie Quarry. left metatarsals I-V. ribs. ribs. seven caudals. ischium. 1997 Erickson. CM 2043 (right tibia. Foster. Foster. ischia. ten dorsals. 11 phalanges. fibula. two ribs. obs.MWC 8028 CM 36034 SMM P90. nine dorsals. pubis. three phalanges. three Bilbey et al. two chevrons. sternal plate. 2003 Erickson. six unguals Femur Left scapula. Haplocanthosaurus? Haplocanthosaurus? Haplocanthosaurus? Haplocanthosaurus? Haplocanthosaurus? Haplocanthosaurus? Haplocanthosaurid indet. 1903c coracoid). priscus) H. juvenile Caudal centrum 25+ caudals Left tibia. phalanges. sacrum. two unguals Mid caudal Four dorsal centra. 2014 McIntosh. femur. five caudals. ilia. 2014. and CM 2046 (left tibia and fibula) Elements Sauropod specimens from the Morrison Formation attributed to Haplocanthosaurus 208 John R. sacrum. chevrons. 2000 unguals. and coracoid Two cervical. 2003 DNM catalog. radii. tial scapula. fibulae. seven dorsals. priscus Identification Reference Hatcher.10 SMM P84. DNM Williams Slow Eagle Utah Wyoming Carnegie Quarry. Foster. right coracoid. humeri. utterbacki (= H. 1903c Table 2 DNM catalog. left scap-coracoid.. Wyoming Red Fork Powder River Quarry B Utah Carnegie Quarry.4 DINO 3017 DINO 4771 DINO 13742 FHPR 1106 Haplocanthosaurus sp. 10 metatarsals. Mathew J. femora. astragalus).37. . with description of a new species. JAIN S... and remarks on the probable habits of the Sauropoda and the age and origin of the Atlantosaurus Beds.000.A. BAKKER R. Journal of Systematic Palaeontology. American Natu ralist. 1986a — Les dinosaurs (Carnosaures.S. DODSON P..R. 2: 1–72. 23: 1–95. FHPR 1106 access thanks to Steve Sroka of the Utah Field House.R. Annales de Paléontologie. ICZN. 20 (supp. FOSTER J.. 1903a — A new sauropod dinosaur from the Jurassic of Colorado. and several other MWC lab volunteers prepared the specimen. with description of Haplocanthosaurus post cranials and a subadult diplodocid skull. Cétiosauridés) du Jurassique moyen de Cerro Cόndor (Chubut. The Mountain Geologist. based on ver- 209 tebral anatomy. CARPENTER K. HALL J. Saurischia): conserved.. FREEMAN V. Access to Haplocanthosaurus specimens CM 572 and CM 879 was courtesy of Matt Lamanna and Dan Pickering of the Carnegie Museum of Natural History. CARPENTER K. 1932 — Die fossile Reptil-Ordnung Saurischia. Monographien zur Geologie und Paläontologie. Colorado.. Mesa Southwest Museum Bulletin... BONAPARTE J.B. HUENE F. Saurischia) of the Morrison Formation and implications for Late Jurassic paleoecology of North America. PABST B. Gunnison.Haplocanthosaurus (Saurischia: Sauropoda) from the lower Morrison Formation (Upper Jurassic) near Snowmass. Big thanks to the many MWC volunteers and staff who helped out with the excavations..L. Rocky Mountain region. KUTTY T. 8: 1–34. Colorado. 1998 — History. In: The beginning of the age of dinosaurs (Ed. 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