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| Rhomaleopakhus turpanensis Upchurch, Mannion, Xu & Barrett, 2021 |
ABSTRACT
Hudiesaurus sinojapanorum is a Late Jurassic sauropod from northwestern China that was erected on the basis of a cervicodorsal vertebra, four teeth, and a nearly complete forelimb. However, re-evaluation of this material, and comparisons with other taxa, indicate that there are few grounds for regarding these specimens as congeneric. Consequently, although we retain the vertebra as the holotype specimen of Hudiesaurus, the forelimb is assigned to a new taxon—Rhomaleopakhus turpanensis, gen. et sp. nov. The teeth previously referred to Hudiesaurus are poorly preserved but resemble those of several other ‘core Mamenchisaurus-like taxa’ (CMTs) from East Asia, such as Mamenchisaurus sinocanadorum. Phylogenetic analyses confirm that Hudiesaurus is a CMT and the sister taxon of Xinjiangtitan. Despite some uniquely shared features, their large size, and close geographic provenance, Hudiesaurus and Xinjiangtitan are retained as distinct genera based on their stratigraphic separation and numerous anatomical differences. Rhomaleopakhus is also shown to be a CMT in all analyses, being most closely related to Chuanjiesaurus and Analong. We link the convergent evolution of robust antebrachia and an enlarged olecranon in CMTs, titanosaurs, and some ornithischians (e.g., ceratopsids) to a more flexed orientation of the forearm, an enhanced role for the forelimb in locomotion, and an anterior shift in the whole-body center of mass. CMTs and titanosaurs potentially converged on a feeding strategy in which the ability to increase browse height via bipedal rearing was sacrificed in return for more efficient locomotion that improved travel between patchily distributed food sources.
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| Holotype right forelimb of Rhomaleopakhus turpanensis gen. et sp. nov. (IVPP V11121-1; holotype) with individual elements in approximate anatomical position, shown in anterior view. |
EUSAUROPODA Upchurch, 1995
MAMENCHISAURIDAE Young and Chao, 1972
RHOMALEOPAKHUS, gen. nov.
RHOMALEOPAKHUS TURPANENSIS, sp. nov.
Etymology—Rhomaleos (ancient Greek, masculine) equals ‘robust’ (pertaining to the body), and pakhus (ancient Greek, masculine) equals ‘forearm.’ The species name refers to the Turpan Basin, China, where the holotype was found.
Paul Upchurch, Philip D. Mannion, Xing Xu and Paul M. Barrett. 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. e1994414. DOI: 10.1080/02724634.2021.1994414
New species of chunky sauropod with a large 'funny bone' described from China
