Open Paleo

Rhomaleopakhus

Upchurch et al., 2021 ro-mah-LAY-oh-PAK-us

From Greek rhomaleos (strong) and pachys (forearm, thick); meaning "strong forearm".

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

Rhomaleopakhus is a genus of mamenchisaurid sauropod dinosaur from the Late Jurassic Kalaza Formation of China. The type and only species is Rhomaleopakhus turpanensis.

Diagnosis

  1. Humeral deltopectoral crest terminates distally in narrow ridge separated from main body by distinct grooves
  2. Prominent ridge projecting posteromedially on posterior surface of radial shaft below proximal end
  3. Radial distal articular surface markedly concave in central and medial portions
  4. One of the most robust ulnae known, with maximum proximal end width to proximodistal length ratio of 0.50
  5. Only non-somphospondylan eusauropod with long-axes of proximal and distal radius surfaces twisted through ~90°

Species

Rhomaleopakhus turpanensis Upchurch et al., 2021

Type species

Named for the Turpan Basin of Xinjiang, China, where the specimen was collected.

Holotype
IVPP V11121-1 , Institute of Vertebrate Paleontology and Paleoanthropology
Material
Right forelimb consisting of humerus, ulna, radius, one carpal, and virtually complete manus
Horizon
lower Kalazha Formation, Kimmeridgian–Tithonian, Late Jurassic , 154.8–143.1 million years ago
Locality
Qiketai, Xinjiang, China

References

  1. Upchurch, P.; Mannion, P. D.; Xu, X.; Barrett, P. M. (2021). Re-assessment of the Late Jurassic eusauropod dinosaur Hudiesaurus sinojapanorum Dong, 1997, from the Turpan Basin, China, and the evolution of hyper-robust antebrachia in sauropods. Journal of Vertebrate Paleontology 41(4). Informa UK Limited. doi:10.1080/02724634.2021.1994414 upchurch2021a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

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

    jones2026b