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Brachiosaurus

Riggs, 1903 BRAK-ee-uh-SOR-uhs /ˌbrækiəˈsɔːrəs/

From Greek 'brachion' (arm) and 'sauros' (lizard); meaning 'arm lizard', referring to its proportionally long forelimbs (the humerus is longer than the femur).

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

Brachiosaurus is the type genus of Brachiosauridae and the iconic giraffe-postured Late Jurassic North American sauropod. The single valid species, Brachiosaurus altithorax, was erected by Elmer S. Riggs in 1903 on a partial postcranial skeleton (FMNH P 25107) from Riggs Quarry No. 13 in the Grand River valley near Grand Junction, Colorado, on the basis of forelimbs longer than hindlimbs and an unusually deep thorax. For nearly a century the African Tendaguru material described by Janensch (1914) as 'Brachiosaurus brancai' was treated as a second species, but Taylor (2009) formally separated it as Giraffatitan brancai on the basis of at least 26 osteological differences across the dorsal vertebrae, caudals, coracoids, humeri, ilia, and femora; the holotype itself is now understood to represent a subadult individual (the coracoid is unfused to the scapula). The Felch Quarry skull (USNM 5730) is tentatively retained in the hypodigm but cannot be confirmed without overlapping material with the holotype. Subsequent splits have separated additional brachiosaurid material into Lusotitan (Portugal) and Vouivria (France), leaving Brachiosaurus monospecific and restricted to the Morrison Formation of the western United States.

Diagnosis

  1. Humerus longer than femur, producing the distinctive giraffe-like upward- sloping body posture.
  2. Posterior dorsal centra subcircular in cross-section; postspinal lamina absent from the dorsal vertebrae.
  3. Posterior dorsal neural spines triangular in lateral view and progressively expand mediolaterally to a petal- or paddle-shaped distal end.
  4. Spinodiapophyseal and spinopostzygapophyseal laminae of middle and posterior dorsal vertebrae contact each other.
  5. Anterior caudal vertebrae bear hyposphenes, have transversely widened neural spines, and lack lateral fossae.
  6. Coracoid elongate along the scapular-suture axis with a glenoid surface directed laterally and mediolaterally broad on a thick buttress.
  7. Tubercle on the dorsal margin of the postacetabular lobe of the ilium.
  8. Femur with tibial and fibular condyles equal in width, fourth trochanter extending to mid-shaft height, and a straight lateral shaft margin.

Species

Brachiosaurus altithorax Riggs, 1903

Type species

From Latin 'altus' (deep) and Greek 'thorax' (chest), referring to the unusually deep thoracic cavity.

Holotype
FMNH P 25107 , Field Museum of Natural History
Material
Partial postcranial skeleton of a subadult individual comprising the last seven dorsal vertebrae, the sacrum, the first two caudal vertebrae, the right humerus, ilium, and femur, the left coracoid, fragments of the left ilium, and dorsal ribs.
Horizon
Morrison Formation, Kimmeridgian–Tithonian, Late Jurassic , 154.8–143.1 million years ago
Locality
Dinosaur Quarry No. 13, near Grand Junction, Colorado, United States

Notable specimens

  • Felch Quarry skull

    YPM 1986, USNM 5730 National Museum of Natural History, Smithsonian Institution Found 1883 by Marshall Parker Felch complementary

    The only skull referred to Brachiosaurus, preserving cranial anatomy absent in the postcranial holotype; reconstructed as the largest sauropod skull from the Morrison Formation. Found by M. P. Felch in Felch Quarry 1 near Garden Park, Colorado; species referral remains uncertain.

    Carpenter & Tidwell (1998)

  • “Toni”

    SMA 0009 Sauriermuseum Aathal ontogeny

    Nearly complete postcranial skeleton of a roughly 2-meter juvenile from the Morrison Formation of the Bighorn Basin, Wyoming; used to reconstruct Brachiosaurus ontogeny, including neck lengthening and humerus changes. Probable referral to B. altithorax was later questioned.

    Carballido et al. (2012)

References

  1. Riggs, E. S. (1904). Structure and relationships of opisthocoelian dinosaurs. Part II, the Brachiosauridae. Field Columbian Museum, Geological Series 2: 229-247.

    Captions the type in place at "Dinosaur Quarry No. 13 near Grand Junction, Colorado".

    riggs1904a
  2. Riggs, E. S. (1903). Brachiosaurus altithorax, the largest known dinosaur. American Journal of Science 15(88): 299-306. American Journal of Science. doi:10.2475/ajs.s4-15.88.299

    Erects Brachiosaurus altithorax on FMNH P 25107 from the Morrison Formation of western Colorado.

    riggs1903a
  3. Carpenter, K.; Tidwell, V. (1998). Preliminary description of a Brachiosaurus skull from Felch Quarry 1, Garden Park, Colorado. Modern Geology 23(1-4): 69-84. carpenter1998b
  4. Taylor, M. P. (2009). A re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropoda) and its generic separation from Giraffatitan brancai (Janensch 1914). Journal of Vertebrate Paleontology 29(3): 787-806. Taylor & Francis. doi:10.1671/039.029.0309

    Formally separates Brachiosaurus altithorax from the Tendaguru taxon (recombined as Giraffatitan brancai); provides the current revised diagnosis and shows the holotype is a subadult.

    taylor2009a
  5. Carballido, J. L.; Marpmann, J. S.; Schwarz-Wings, D.; Pabst, B. (2012). New information on a juvenile sauropod specimen from the Morrison Formation and the reassessment of its systematic position. Palaeontology 55(2): 567-582. doi:10.1111/j.1475-4983.2012.01139.x carballido2012b
  6. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026b
  7. Janensch, W. (1914). Übersicht über die Wirbeltierfauna der Tendaguru-Schichten [Overview of the vertebrate fauna of the Tendaguru beds]. Archiv für Biontologie 3: 81-110.

    Described the Tendaguru material as Brachiosaurus brancai, later Giraffatitan.

    janensch1914a