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Diplodocus

Marsh, 1878 di-PLOD-o-kus /dɪˈplɒdəkəs/

From Greek 'diplos' (double) and 'dokos' (beam), referring to the double-beamed chevrons of the tail (with both anterior and posterior rami) that distinguished the genus when Marsh erected it in 1878.

154.8–143.1 million years ago Kimmeridgian–Tithonian, Late Jurassic
Late Jurassic stages

Diplodocus is the type genus of Diplodocidae and one of the most iconic and best-known sauropod dinosaurs of the Late Jurassic Morrison Formation of western North America. Othniel Charles Marsh erected the genus in 1878 on a partial tail and posterior limb (YPM 1920) collected near Cañon City, Colorado, by S. W. Williston, designating Diplodocus longus as the type species. John Bell Hatcher (1901) produced the first comprehensive osteological monograph of the genus based on the near-complete Carnegie Museum specimens CM 84 and CM 94 from Sheep Creek in Albany County, Wyoming, and named those Carnegie skeletons as a new species, Diplodocus carnegii — the basis of the famous "Dippy" cast that Andrew Carnegie distributed to museums worldwide. Tschopp, Mateus and Benson (2015) reassessed all diplodocid material at the specimen level, argued that the fragmentary D. longus holotype was a nomen dubium, and applied to the ICZN to switch the type species to D. carnegii. The Commission ultimately ruled against the proposal in Opinion 2425 (2018), voting 16-4 to maintain D. longus as the type species. The same Tschopp and colleagues analysis kept Seismosaurus hallorum (Gillette, 1991) in Diplodocus as its own species, D. hallorum, and reassigned D. hayi (Holland, 1924) to the new genus Galeamopus, leaving D. longus, D. carnegii, and D. hallorum as the three currently valid Diplodocus species.

Diagnosis

  1. Anteriorly inclined base of the posterior dorsal neural spines (unique within Diplodocinae).
  2. Transition from fan-shaped to normal caudal ribs occurs at or posterior to caudal vertebra 7-8 (unique among Diplodocidae).
  3. Pneumatopores of anterior caudal centra persist through caudal vertebra 16 or more posteriorly (unique among Diplodocoidea).
  4. Mid-caudal centra with trapezoidal articular surfaces (unique among Flagellicaudata).
  5. Last caudal ribs occur on caudal vertebra 18 or more posteriorly.
  6. Iliac blade height above the pubic peduncle ≥ 0.40 of its anteroposterior length (unique within Diplodocinae).
  7. Anteromedially directed crest on the proximal fibula extending into a notch behind the cnemial crest of the tibia (unique within Diplodocinae).
  8. Chevrons of the tail double-beamed (with both anterior and posterior rami) — Marsh's original diagnostic character and the source of the generic name.

Species (3)

Diplodocus longus Marsh, 1878

Type species

From Latin 'longus' (long), referring to the long tail of the holotype.

Holotype
YPM 1920 , Yale Peabody Museum of Natural History
Material
Posterior limb (femur, tibia, fibula) and tail with chevrons of a single individual; the tail is reduced to roughly two near- complete caudal vertebrae as currently preserved.
Horizon
Morrison Formation, Kimmeridgian–Tithonian, Late Jurassic , 154.8–143.1 million years ago
Locality
Felch Quarry 1, Garden Park, Colorado, United States

Diplodocus carnegii Hatcher, 1901

Honors Andrew Carnegie, the Pittsburgh industrialist and patron of the Carnegie Museum of Natural History whose funding sent collectors to the Sheep Creek quarry.

Holotype
CM 84 , Carnegie Museum of Natural History
Material
Articulated partial skeleton — 41 axial vertebrae (axis through caudal 12), pelvis, right femur, right scapulocoracoid, and 18 ribs; CM 94 (a more complete pelvis, hindlimb, and right pes) was designated cotype.
Horizon
middle Morrison Formation, Kimmeridgian–Tithonian, Late Jurassic , 154.8–143.1 million years ago
Locality
Sheep Creek, Camp Carnegie quarry, Quarry D(3), Wyoming, United States

Diplodocus hallorum (Gillette, 1991)

First named as Seismosaurus halli

Honors James and Ruth Hall of the Ghost Ranch Conference Center, New Mexico, for their support of regional paleontology.

Holotype
NMMNH 3690 , New Mexico Museum of Natural History and Science
Material
Partially articulated skeleton: dorsal vertebrae and ribs, both ilia and ischia, a pubis, sacrum, caudal vertebrae, five chevrons, and 230 gastroliths.
Horizon
upper Brushy Basin Member, Morrison Formation, Kimmeridgian–Tithonian, Late Jurassic , 154.8–143.1 million years ago
Locality
Seismosaurus Quarry, New Mexico, United States
Diagnosis
  1. Dorsal end of the postspinal lamina of single dorsal neural spines concave transversely
  2. Mid-caudal neural arches situated on the anterior half of the centrum
  3. Vertical mid-caudal neural spines (more posteriorly inclined in D. carnegii)
  4. Posterior end of the mid- and posterior caudal neural spine summits lies more or less straight above the postzygapophyses
  5. Distinct fossae on the medial surfaces of the proximal branches of the middle chevrons
  6. Gracile femur, with a robustness index below 0.22

Synonyms

  • Seismosaurus halli reassigned

    Original binomial (Gillette, 1991) for the holotype; the epithet was emended to hallorum (Gillette, 1994) for Latin grammar.

  • Seismosaurus hallorum reassigned

    Emended combination (Gillette, 1994); recombined as Diplodocus hallorum when Seismosaurus was synonymized with Diplodocus, a synonymy Tschopp, Mateus and Benson (2015) upheld.

Notable specimens

  • AMNH FR 223

    American Museum of Natural History Found 1897 by Barnum Brown and Henry Osborn historic

    Semi-articulated partial postcranial skeleton from Como Bluff, collected 1897; the first Diplodocus mount made and the first well-preserved individual skeleton of the genus discovered. Later found to belong to D. hallorum and to be the geologically youngest specimen of that species.

    Tschopp et al. (2015)Osborn (1899)

  • CM 11255

    Carnegie Museum of Natural History ontogeny

    Juvenile skull whose snout was not blunt and whose teeth were not confined to the front of the snout, differing greatly from adult Diplodocus skulls. The differences indicate adults and juveniles fed differently, an ecological difference not previously observed in sauropodomorphs.

    Whitlock et al. (2010)

  • NMMNH 3690

    New Mexico Museum of Natural History and Science Found 1985 gut contents

    Semi-articulated partial skeleton from near San Ysidro, New Mexico, preserving 230 gastroliths along with vertebrae, partial pelvis, and right femur. Originally named Seismosaurus, it was later referred to Diplodocus hallorum.

    Tschopp et al. (2015)Gillette (1994)

  • CT-30 specimen

    MAP-4497, MAP-4498, MAP-4499, MAP-4500, MAP-4501, MAP-4502, MAP-4503, MAP-4504, MAP-4506, MAP-6177, MAP-6178, MAP-6179, MAP-6180, MAP-6181, MAP-6182, MAP-6183, MAP-6184, MAP-6185, MAP-6186, MAP-6187, MAP-6188, MAP-6189, MAP-6190, MAP-6191, MAP-6192, MAP-6193, MAP-6194, MAP-6195, MAP-6196, MAP-6197, MAP-6200 Museo de la Fundación Conjunto Paleontológico de Teruel-Dinópolis Found 2008 range extension

    Partial tail of 14 caudal vertebrae and 15 chevrons from the Late Jurassic Villar del Arzobispo Formation of Teruel, Spain, referred to Diplodocus sp. and the first evidence of the genus outside North America. Phylogenetic analyses recover it as the sister of D. hallorum.

    Sánchez-Fenollosa et al. (2026)

References

  1. Marsh, O. C. (1878). Principal characters of American Jurassic dinosaurs, Part I. American Journal of Science 16(95): 411-416. American Journal of Science. doi:10.2475/ajs.s3-16.95.411

    Erects Diplodocus longus on YPM 1920 from the Morrison Formation of Cañon City, Colorado, and formally proposes the suborder Sauropoda.

    marsh1878b
  2. Hatcher, J. B. (1901). Diplodocus (Marsh): its osteology, taxonomy, and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1: 1-63. Carnegie Institute. doi:10.5962/p.234818

    First comprehensive osteology of the genus; names Diplodocus carnegii on CM 84 (cotype CM 94) from Sheep Creek, Wyoming — the Carnegie skeleton famously cast as 'Dippy' for distribution to museums.

    hatcher1901a
  3. Tschopp, E.; Mateus, O.; Benson, R. B. J. (2015). A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda). PeerJ 3: e857. PeerJ. doi:10.7717/peerj.857

    Specimen-level phylogenetic revision; provides the modern revised diagnosis and proposes switching the type species to D. carnegii (subsequently rejected by ICZN Opinion 2425).

    tschopp2015a
  4. International Commission on Zoological Nomenclature (2018). Opinion 2425. Diplodocus Marsh, 1878 (Dinosauria, Sauropoda): Diplodocus longus Marsh, 1878 maintained as the type species. Bulletin of Zoological Nomenclature 75: a062. International Trust for Zoological Nomenclature. doi:10.21805/bzn.v75.a062

    Resolves Case 3700 (Tschopp and Mateus, 2016 application). The Commission voted 16-4-1 against using plenary power to switch the type species; D. longus is maintained as the type of Diplodocus.

    iczn2018a
  5. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

    Source of the body length, mass, and hip height estimates, and the appearance features.

    jones2026b
  6. Osborn, H. F. (1899). A skeleton of Diplodocus, recently mounted in the American Museum. Science 10(259): 870-874. osborn1899a
  7. Whitlock, J. A.; Wilson, J. A.; Lamanna, M. C. (2010). Description of a nearly complete juvenile skull of Diplodocus (Sauropoda: Diplodocoidea) from the Late Jurassic of North America. Journal of Vertebrate Paleontology 30(2): 442-457. doi:10.1080/02724631003617647 whitlock2010a
  8. Gillette, D. D. (1994). Seismosaurus: The Earth Shaker. Columbia University Press, New York. gillette1994a
  9. Gillette, D. D. (1991). Seismosaurus halli, gen. et sp. nov., a new sauropod dinosaur from the Morrison Formation (Upper Jurassic/Lower Cretaceous) of New Mexico, USA. Journal of Vertebrate Paleontology 11(4): 417-433. Informa UK Limited. doi:10.1080/02724634.1991.10011413

    Named Seismosaurus halli, later recombined as Diplodocus hallorum.

    gillette1991a
  10. Holland, W. J. (1924). The skull of Diplodocus. Memoirs of the Carnegie Museum 9(3): 379-403. doi:10.5962/p.234841

    Described Diplodocus hayi, later moved to Galeamopus.

    holland1924a
  11. Sánchez-Fenollosa, S.; García-Cobeña, J.; Cobos, A. (2026). Intercontinental evidence of the iconic genus Diplodocus Marsh, 1878 (Dinosauria, Sauropoda). Journal of Vertebrate Paleontology e2718423. Informa UK Limited. doi:10.1080/02724634.2026.2718423

    Describes the CT-30 specimen from Teruel, the first record of Diplodocus outside North America.

    sánchez-fenollosa2026a
  12. Tschopp, E.; Mateus, O. (2016). Case 3700 Diplodocus Marsh, 1878 (Dinosauria, Sauropoda): proposed designation of D. carnegii Hatcher, 1901 as the type species. Bulletin of Zoological Nomenclature 73(1): 17-24. doi:10.21805/bzn.v73i1.a22 tschopp2016a