Camarasaurus grandis
Temporal range: Late Jurassic,
Cast of a Camarasaurus grandis skull at the Dinosaur Journey Museum.
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: †Sauropodomorpha
Clade: †Sauropoda
Clade: †Macronaria
Family: †Camarasauridae
Genus: †Camarasaurus
Species:
†C. grandis
Binomial name
†Camarasaurus grandis
(Marsh, 1877)
Synonyms
  • Amphicoelias latus?
    Cope, 1877
  • Apatosaurus grandis
    Marsh, 1877
  • Morosaurus grandis
    (Marsh, 1877) Marsh, 1878
  • Morosaurus impar
    Marsh, 1878
  • Morosaurus robustus
    Marsh, 1878
  • Pleurocoelus montanus
    Marsh, 1896
  • Camarasaurus impar
    (Marsh, 1878) Gilmore, 1925
  • Camarasaurus robustus
    (Marsh, 1878) Gilmore, 1925
  • Cathetosaurus lewisi?
    Jensen, 1988
  • Camarasaurus lewisi?
    (Jensen, 1988) McIntosh, 1990

Camarasaurus grandis is an extinct species of sauropod dinosaur in the genus that lived during the Jurassic in what is now the western United States. It is the geologically oldest of the four species of the genus Camarasaurus.

Taxonomy

Camarasaurus grandis was named by Othniel Charles Marsh in 1877. It is one of four valid species of Camarasaurus, alongside Camarasaurus lentus, Camarasaurus lewisi, and Camarasaurus supremus.[1] The type specimen of Camarasaurus grandis is the holotype YPM 1901, a partial skeleton of an immature individual from Como Bluff, Wyoming.[1]

Camarasaurus grandis is regarded as having three junior synonyms: Morosaurus impar, Morosaurus robustus, and Pleurocoelus montanus.[2][3][1] One of these junior synonyms, M. impar, is the type species of Morosaurus, the genus to which C. grandis and C. lentus were assigned until it was synonymized with Camarasaurus.[4] Amphicoelias latus, which is conventionally regarded as a synonym of C. supremus, may also be synonymous with C. grandis, based on where its type specimen was found.[5] C. grandis's contemporary, C. lewisi, may also be synonymous with Camarasaurus grandis.[1] The holotype of C. lentus may be a specimen of C. grandis, rather than the species conventionally known as C. lentus.[1]

There are numerous specimens of Camarasaurus grandis, and the majority of the skeleton is known.[1][6]

Description

Camarasaurus grandis was a moderately-sized member of its genus, similar in size to C. lentus but smaller than C. supremus. Gregory S. Paul estimated its length as 14 metres (46 ft) and mass as 13 tonnes,[6] whereas John Foster estimated its length as 15 metres (49 ft) and mass as 12.6 tonnes for an average-sized individual, with large individuals reaching over 16.5 tonnes.[7]

The anterior dorsal vertebrae of Camarasaurus grandis are one of the most distinctive parts of the skeleton. The vertebrae are much taller than in C. lentus and C. supremus.[1] The vertebrae are also unusual in the position of the connections between the neural arch and centrum, known as the neurocentral synostoses.[8] In most reptiles, including Camarasaurus lentus, the neurocentral synostoses lie at the level of the ventral margin of the neural arch.[9][7] In contrast, in C. grandis, the neurocentral synostoses are elevated above the level of the neural canal,[7] with raised pedicels on the centrum separating the neural arch from the articular faces of the centrum.[10] The centrum can completely surround the canal, resulting in a neural arch that does not actually form an arch over the neural canal.[9] This characteristic is only visible in juveniles.[7]

C. grandis differs from C. lentus in having T-shaped expansions of its anterior caudal neural spines.[1]

History of study

Forelimb of Camarasaurus grandis mounted at the Field Museum in 1901.

In 1877 during the Yale Peabody Museum’s expedition to Como Bluff, William Harlow Reed and several other field workers for Othniel Charles Marsh collected a basioccipital and partial postcranial skeleton. Camarasaurus grandis was named by Marsh in 1877 on the specimen (YPM 1901). He initially considered it a species of Apatosaurus.[11] The next year, Marsh named another new species, Morosaurus impar,[12] and shortly thereafter reclassified Apatosaurus grandis as Morosaurus grandis and named a third species, Morosaurus robustus.[13] The type specimens of M. impar and M. robustus could be from the same individual as YPM 1901. Additional material of C. lentus would be collected between 1877 and 1879 by YPM crews, including some skull material. In 1896, Marsh named another species of Sauropod from Como Bluff, Pleurocoelus montanus, based on a fragmentary postcranial skeleton of a juvenile from. The species was later synonymized with C. grandis. All of the material found at Como Bluff came from the Kimmeridgian of the Morrison Formation.

During the Second Dinosaur Rush in 1900, crews of the Field Museum of Natural History collected several appendicular and axial elements, including a nearly complete forelimb, near Fruita, Colorado. The C. grandis material from Fruita led to new reconstructions of Sauropod manus and pes structure. In 1898, Samuel Wendell Williston regarded M. impar as synonymous with M. grandis.[14] In 1901, Elmer Riggs recognized that Morosaurus was a junior synonym of Camarasaurus.[4] C. robustus was suggested to be synonymous with C. grandis in 1930 by Richard S. Lull.[15] In 1958, Theodore E. White synonymized C. grandis with C. supremus.[16] This proposed synonymy has not been upheld by subsequent study.

A specimen of Camarasaurus grandis was excavated in New Mexico in 1978, and was one of the first partial skeletons from the Morrison Formation to be excavated in the state.[17] It was initially reported as a specimen of C. cf. supremus in 1982, but reinterpreted as C. grandis in 2005.[1]

A relatively complete skeleton of Camarasaurus grandis, GMNH-PV 101, was described in 1996.[18] However, an unpublished study by Emanuel Tschopp and colleagues presented at the 2014 meeting of the Society of Vertebrate Paleontology suggested that this specimen may have closer affinities to Camarasaurus lewisi, which they argued represented a distinct genus, Cathetosaurus.[19]

Paleoecology

Camarasaurus grandis lived during the Kimmeridgian age of the Jurassic in what is now Wyoming, Colorado, and New Mexico.[1] It is one of the more common species of Camarasaurus, with 9.1% of known Camarasaurus specimens identified as C. grandis (the majority of specimens cannot be identified as belonging to any particular species).[20]

A specimen of C. grandis[1] from New Mexico showed signs of having been fed on by Allosaurus.[17]

Camarasaurus grandis is the geologically oldest species of Camarasaurus, and may be ancestral to the later species of the genus.[6]

References

  1. 1 2 3 4 5 6 7 8 9 10 11 Ikejiri, T. (2005). "Distribution and biochronology of Camarasaurus (Dinosauria, Sauropoda) from the Jurassic Morrison Formation of the Rocky Mountain Region". New Mexico Geological Society Field Conference Guidebook, Geology of the Chama Basin. Vol. 56. pp. 367–379.
  2. ↑ McIntosh, J. S. (1990). "Sauropoda". In Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.). The Dinosauria (1 ed.). Berkeley: University of California Press. pp. 345–401.
  3. ↑ Upchurch, Paul; Barrett, Paul M.; Dodson, Peter (2004). "Sauropoda". In Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.). The Dinosauria (2 ed.). Berkeley: University of California Press. pp. 259–322. ISBN 0-520-24209-2.
  4. 1 2 Riggs, E. S. (1901). "The fore leg and pectoral girdle of Morosaurus": 275–281. {{cite journal}}: Cite journal requires |journal= (help)
  5. ↑ Carpenter, K. (1998). "Vertebrate biostratigraphy of the Morrison Formation near Cañon City, Colorado". Modern Geology. 23: 407–426.
  6. 1 2 3 Paul, G. S. (2016). The Princeton Field Guide to Dinosaurs (2nd ed.). Princeton and Oxford: Princeton University Press. ISBN 978-0-691-16766-4.
  7. 1 2 3 4 Foster, J. R. (2020). Jurassic West: the dinosaurs of the Morrison Formation and their world. Life of the past (2nd ed.). Bloomington, Indiana: Indiana University Press. ISBN 978-0-253-05158-5.
  8. ↑ Wedel, Matt (2012-04-09). "Neural spine bifurcation in sauropods, Part 2: why serial position matters". Sauropod Vertebra Picture of the Week.
  9. 1 2 Wedel, Matt (2017-05-31). "Sauropod neural canals are weird, part 1: when the neural arch, um, isn't one". Sauropod Vertebra Picture of the Week.
  10. ↑ Marsh, O. C. (1889). "Notice of new American Dinosauria". American Journal of Science. 37 (220): 331–336. Bibcode:1889AmJS...37..331M. doi:10.2475/ajs.s3-37.220.331. S2CID 131729220.
  11. ↑ Marsh, Othniel Charles (1877). "Notice of new dinosaurian reptiles from the Jurassic Formation". American Journal of Science. s3-14 (84): 514–516. Bibcode:1877AmJS...14..514M. doi:10.2475/ajs.s3-14.84.514. S2CID 130488291. Retrieved 2017-03-11.
  12. ↑ Marsh, O. C. (1878). "Notice of new dinosaurian reptiles". American Journal of Science. 15 (87): 241–244.
  13. ↑ Marsh, O. C. (1878). "Principal characters of American Jurassic dinosaurs". American Journal of Science. 3. 16: 411–416.
  14. ↑ Williston, S. W. (1898). "The sacrum of Morosaurus". Kansas University Quarterly. 7 (3): 173–175.
  15. ↑ Lull, Richard S. (1930). "Skeleton of Camarasaurus lentus recently mounted at Yale". American Journal of Science. 14 (109): 1–5. Bibcode:1930AmJS...19....1L. doi:10.2475/ajs.s5-19.109.1.
  16. ↑ White, Theodore E. (1958). "The braincase of Camarasaurus lentus (Marsh)". Journal of Paleontology. 32 (3): 477–494. JSTOR 1300674.
  17. 1 2 Rigby, J. K. (1982). "Camarasaurus cf. supremus from the Morrison Formation near San Ysidro, New Mexico—the San Ysidro dinosaur": 271–272. {{cite journal}}: Cite journal requires |journal= (help)
  18. ↑ McIntosh, John S.; Miles, Clifford A.; Cloward, Karen C.; Parker, Jeffrie R. (1996-12-24). "A new nearly complete skeleton of Camarasaurus". Bulletin of Gunma Museum of Natural History. 1: 1–87. ISSN 1342-4092.
  19. ↑ Tschopp, E.; Mateus, O.; Kosma, R.; Sander, P. M.; Joger, U.; Wings, O. W. M. (2014). "A specimen-level cladistic analysis of Camarasaurus (Dinosauria, Sauropoda) and a revision of camarasaurid taxonomy" (PDF). Meeting Program and Abstracts. 74th Annual Meeting of the Society of Vertebrate Paleontology. Berlin. p. 241.
  20. ↑ Woodruff, D. Cary; Foster, John R. (2017-05-31). "The first specimen of Camarasaurus (Dinosauria: Sauropoda) from Montana: The northernmost occurrence of the genus". PLOS ONE. 12 (5): e0177423. Bibcode:2017PLoSO..1277423W. doi:10.1371/journal.pone.0177423. ISSN 1932-6203. PMC 5451207. PMID 28562606.
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