Open Paleo

Atlasaurus

Monbaron et al., 1999 AT-luh-SAWR-us

Named for the Atlas Mountains of North Africa, where its fossils were found, combined with Greek 'sauros' meaning 'lizard'.

168.2–165.3 million years ago Bathonian, Middle Jurassic
Middle Jurassic stages

Atlasaurus is a genus of sauropod dinosaurs from Middle Jurassic (Bathonian to Callovian stages) beds in North Africa.

Under dispute

The affinities of Atlasaurus are contested and unresolved. The dedicated titanosauriform analyses of D'Emic (2012) and Mannion and colleagues (2013) recover it as a non-neosauropod eusauropod, outside Macronaria, whereas Moore and colleagues (2020) recover it variably as a non-neosauropod eusauropod (equal weighting), a brachiosaurid (implied weighting), or a basal macronarian (Bayesian). Its describers (Monbaron and colleagues, 1999) originally interpreted it as a brachiosaurid; Jones (2026) treats its affinities as ambiguous.

Diagnosis

  1. Supratemporal fenestra twice as wide as long (140 by 70 mm), not visible in lateral perspective
  2. Combined width of paroccipital processes 48% of estimated mandible length; processes extend horizontally at nearly right angles to skull long axis
  3. Mandibular symphysis and dentary very shallow (symphyseal depth 116% minimum depth of dentary)
  4. Humerus length 65% of estimated dorsal vertebral series length
  5. Ulna length exceeds tibia length by approximately 115%

Species

Atlasaurus imelakei Monbaron et al., 1999

Type species

From Arabic 'imelakei' meaning 'giant', reflecting the large size of the animal.

Holotype
Not catalogued , Service Géologique du Maroc, Ministére de l’Energie et des Mines (uncatalogued)
Material
Nearly complete skeleton including skull, cervical and dorsal vertebrae, sacrum, caudal vertebrae, forelimbs, hindlimbs, and manus.
Horizon
Grès des Guettioua Formation, Bathonian, Middle Jurassic , 168.2–165.3 million years ago
Locality
Wawmda, Azilal, Morocco

References

  1. Monbaron, M.; Russell, D. A.; Taquet, P. (1999). Atlasaurus imelakei n.g., n.sp., a brachiosaurid-like sauropod from the Middle Jurassic of Morocco alen. Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science 329(7): 519-526. Elsevier BV. doi:10.1016/s1251-8050(00)80026-9 monbaron1999a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

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

    jones2026b
  3. Moore, A. J.; Upchurch, P.; Barrett, P. M.; Clark, J. M.; Xu, X. (2020). Osteology of Klamelisaurus gobiensis (Dinosauria, Eusauropoda) and the evolutionary history of Middle-Late Jurassic Chinese sauropods. Journal of Systematic Palaeontology 18(16): 1299-1393. doi:10.1080/14772019.2020.1759706

    Recovered Atlasaurus variably as a non-neosauropod eusauropod (equal weighting), a brachiosaurid (implied weighting), or a basal macronarian (Bayesian).

    moore2020a
  4. D'Emic, M. D. (2012). The early evolution of titanosauriform sauropod dinosaurs. Zoological Journal of the Linnean Society 166: 624-671. doi:10.1111/j.1096-3642.2012.00853.x

    Recovered Atlasaurus as the sister taxon to Neosauropoda — a non-neosauropod eusauropod, outside Macronaria — statistically rejecting a brachiosaurid position.

    d'emic2012b
  5. Mannion, P. D.; Upchurch, P.; Barnes, R. N.; Mateus, O. (2013). Osteology of the Late Jurassic Portuguese sauropod dinosaur Lusotitan atalaiensis (Macronaria) and the evolutionary history of basal titanosauriforms. Zoological Journal of the Linnean Society 168(1): 98-206. Oxford University Press (OUP). doi:10.1111/zoj.12029

    Recovered Atlasaurus as a non-neosauropod eusauropod outside Macronaria.

    mannion2013a