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Haplocanthosaurus

Hatcher, 1903 hap-lo-KAN-tho-SAWR-us

Simple spined lizard; from Greek haploos (simple), akantha (spine or thorn), and sauros (lizard)

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

Haplocanthosaurus is a genus of diplodocoid sauropod dinosaur. Two species, H. delfsi and H. priscus, are known from incomplete fossil skeletons. They lived during the Late Jurassic (Kimmeridgian stage), 155 to 152 million years ago in North America. The type species is H. priscus, named in 1903 John Bell Hatcher , and the referred species H. delfsi was discovered by a young college student named Edwin Delfs in Colorado, United States and described by Jack McIntosh and Michael Williams in 1988. Haplocanthosaurus specimens have been found in the lowermost layer of the Morrison Formation, along with Hesperosaurus mjosi, Brontosaurus yahnahpin, and Allosaurus jimmadseni.

Under dispute

Haplocanthosaurus is recovered as the earliest diplodocoid by some analyses (Whitlock, 2011; Tschopp and colleagues, 2015; Mannion and colleagues, 2019), but as a basal macronarian or an unplaced neosauropod outside Diplodocoidea by others (Läng and Mahammed, 2010; Carballido and colleagues, 2011; Britt and colleagues, 2017; Gomez and colleagues, 2024), and Mannion and colleagues (2011) recover it outside Neosauropoda in some of their trees. Its position is weakly supported throughout.

Diagnosis

  1. Cervical vertebrae of only moderate length with prominent but simple pleurocoels; neural spines of posterior cervicals and anterior dorsals undivided.
  2. Dorsal centra relatively small with prominent pleurocoels; dorsal arches high with diapophyses directed upward at 45 degrees as well as outward; spines short and broad.
  3. Sacrum of five vertebrae (dorso-sacral, three primary sacrals, caudo- sacral) with coossified centra and sacral ribs forming a yoke; spines with tendency toward coalescence particularly in sacrals one through three.
  4. Caudal centra amphicoelous, short, without pleurocentral cavities; chevron facets very prominent giving the underside of each centrum a sculptured appearance; anterior caudal spines slender and curved backward.
  5. Distal end of scapula thin and broadly splayed; proximal plate relatively small; sternal plates large and subquadrangular.
  6. Ischium shaft straight with distal end slightly broadened but not thickened; femur with latero-medial shaft diameter significantly exceeding the antero-posterior diameter.

Species (2)

Haplocanthosaurus priscus (Hatcher, 1903)

Type species

First named as Haplocanthus priscus

From Latin 'priscus' meaning 'ancient' or 'primitive', reflecting the recognition of this sauropod as a particularly early or primitive member of its lineage.

Holotype
CM 572 , Carnegie Museum of Natural History
Material
Two posterior cervicals, ten dorsals, five sacrals with ilia, ischia and pubes, nineteen anterior caudals, two chevrons, a nearly complete series of ribs, and a femur.
Horizon
Morrison Formation, Kimmeridgian–Tithonian, Late Jurassic , 154.8–143.1 million years ago
Locality
Marsh-Felch Quarry, Colorado, United States The Marsh-Felch Quarry and the CMNH Quarry, the locality for H. delfsi, both lie in the Garden Park district, less than a mile apart and worked 53 years apart.

Synonyms

  • Haplocanthus priscus preoccupied

    Original combination (Hatcher, 1903a). The genus name Haplocanthus is preoccupied by a fish and was replaced in the same volume by Haplocanthosaurus (Hatcher, 1903b).

Haplocanthosaurus delfsi McIntosh & Williams, 1988

Named for Edwin Delfs, the college student who discovered the holotype specimen in Colorado.

Holotype
CMNH 10380 , Cleveland Museum of Natural History
Material
Cervicals 1 to 4; nine posterior dorsals with left-side ribs; five sacrals; caudals 1 to 14; several chevrons; left scapula shaft and distal end; fragmentary coracoid; right sternal plate; proximal left radius and ulna; both ilia; left pubis; left ischium; left femur.
Horizon
lower Morrison Formation, Oxfordian–Berriasian, Late Jurassic–Early Cretaceous , 161.5–137.1 million years ago The age of the containing rock unit; no finer age has been published.
Locality
CMNH Quarry, Colorado, United States
Diagnosis
  1. V-shaped, anterolaterally projecting laminae present on neural spines of the middle dorsal vertebrae.
  2. Distal end of ischium not rotated inward and not fused to its opposite member in the midline.

Synonyms of the genus

Name Type Reason
Haplocanthus preoccupied Name preoccupied by Haplocanthus (Pisces).

References

  1. Hatcher, J. B. (1903). A new sauropod dinosaur from the Jurassic of Colorado. Proceedings of the Biological Society of Washington 16: 1-2.

    Erects Haplocanthus priscus on a partial Morrison skeleton; Haplocanthus was later replaced by Haplocanthosaurus in Hatcher (1903b), later in the same volume.

    hatcher1903a
  2. Hatcher, J. B. (1903). A new name for the dinosaur Haplocanthus Hatcher. Proceedings of the Biological Society of Washington 16: 100.

    Replaces the preoccupied generic name Haplocanthus with Haplocanthosaurus.

    hatcher1903b
  3. McIntosh, J. S.; Williams, M. E. (1988). A new species of sauropod dinosaur, Haplocanthosaurus delfsi sp. nov., from the Upper Jurassic Morrison Formation of Colorado. Kirtlandia 43: 3-26.

    Describes the second species H. delfsi on a ~21 m mounted skeleton from the lower Morrison of Oil Creek, Colorado; presents a revised genus diagnosis.

    mcintosh1988a
  4. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

    Source of the hip height estimate.

    jones2026b
  5. Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.

    Source of the mass estimate.

    paul2024a
  6. Whitlock, J. A. (2011). A phylogenetic analysis of Diplodocoidea (Saurischia: Sauropoda). Zoological Journal of the Linnean Society 161(4): 872-915. doi:10.1111/j.1096-3642.2010.00665.x

    Recovered Haplocanthosaurus as the basalmost diplodocoid.

    whitlock2011a
  7. 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

    Recovered Haplocanthosaurus as the earliest diplodocoid under implied weights.

    tschopp2015a
  8. Mannion, P. D.; Upchurch, P.; Schwarz, D.; Wings, O. (2019). Taxonomic affinities of the putative titanosaurs from the Late Jurassic Tendaguru Formation of Tanzania: phylogenetic and biogeographic implications for eusauropod dinosaur evolution. Zoological Journal of the Linnean Society 185(3): 784-909. Oxford University Press (OUP). doi:10.1093/zoolinnean/zly068

    Recovered Haplocanthosaurus as a basal diplodocoid.

    mannion2019a
  9. Läng, É.; Mahammed, F. (2010). New anatomical data and phylogenetic relationships of Chebsaurus algeriensis (Dinosauria, Sauropoda) from the Middle Jurassic of Algeria. Historical Biology 22(1-3): 142-164. Taylor & Francis. doi:10.1080/08912960903515570

    Recovered Haplocanthosaurus as a basal macronarian, with Atlasaurus.

    läng2010a
  10. Carballido, J. L.; Rauhut, O. W. M.; Pol, D.; Salgado, L. (2011). Osteology and phylogenetic relationships of Tehuelchesaurus benitezii (Dinosauria, Sauropoda) from the Upper Jurassic of Patagonia. Zoological Journal of the Linnean Society 163(2): 605-662. Wiley. doi:10.1111/j.1096-3642.2011.00723.x

    Recovered Haplocanthosaurus as a basal macronarian.

    carballido2011a
  11. Britt, B. B.; Scheetz, R. D.; Whiting, M. F.; Wilhite, D. R. (2017). Moabosaurus utahensis, n. gen., n. sp., a new sauropod from the Early Cretaceous (Aptian) of North America. Contributions from the Museum of Paleontology, University of Michigan 32(11): 189-243. https://hdl.handle.net/2027.42/136227

    Recovered Haplocanthosaurus in a basal neosauropod polytomy outside Diplodocoidea.

    britt2017a
  12. Gomez, K. L.; Carballido, J. L.; Pol, D. (2024). Cranial anatomy of Bagualia alba (Dinosauria, Eusauropoda) from the Early Jurassic of Patagonia and the implications for sauropod cranial evolution. Journal of Systematic Palaeontology 22(1): 2400471. doi:10.1080/14772019.2024.2400471

    Recovered Haplocanthosaurus as the earliest macronarian.

    gomez2024a
  13. Mannion, P. D.; Upchurch, P.; Mateus, O.; Barnes, R. N.; Jones, M. E. H. (2011). New information on the anatomy and systematic position of Dinheirosaurus lourinhanensis (Sauropoda: Diplodocoidea) from the Late Jurassic of Portugal, with a review of European diplodocoids. Journal of Systematic Palaeontology 10(3): 521-551. Informa UK Limited. doi:10.1080/14772019.2011.595432

    Recovered Haplocanthosaurus variously as a basal diplodocoid, a macronarian, or a basal eusauropod across its most parsimonious trees.

    mannion2011a