Rhomaleopakhus

Rhomaleopakhus Temporal range: Late Jurassic 145 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	†Sauropodomorpha
Clade:	†Sauropoda
Family:	†Mamenchisauridae
Genus:	†Rhomaleopakhus Upchurch et al., 2021
Species:	†R. turpanensis
Binomial name
†Rhomaleopakhus turpanensis Upchurch et al., 2021

Rhomaleopakhus (meaning "strong forearm") is a genus of mamenchisaurid sauropod, dinosaur from the Late Jurassic Kalaza Formation of China. The type and only species is Rhomaleopakhus turpanensis.^[1]

The holotype IVPP-V11121-1, was found by a Chinese-Japanese Chunichi Shinibun expedition near Qiketai in Shanshan, Xinjiang province in 1993, along with the holotype of Hudiesaurus,^[2] and is a partially complete forelimb consisting of a humerus, ulna, radius, one carpal, and a partially complete manus that was originally assigned to the coeval mamenchisaurid Hudiesaurus.^[2] Paul Upchurch in 2004 rejected the identity because of a lack of overlapping material.^[3] However, in a 2021 reassessment of the latter genus, the forelimb was separated from its hypodigm and named the holotype of a new genus and species, Rhomaleopakhus turpanensis; the specific name refers to the Turpan Basin where the specimen was collected.^[1]

Upchurch et al. note that the robustness of the forelimb, after which the taxon was named, convergently evolved in what are called the "Core Mamenchisaurus-like taxa" (CMTs),^[4] titanosaurs, and ceratopsids. They believe this correlates with a more flexed orientation of the forearm, an enhanced role of the forearm in feeding, and a more anterior shift in the center of mass. It is possible that CMTs and titanosaurs specialized in a feeding strategy that involved efficient locomotion between sparsely-located food sources.^[1]

Upchurch et al. used Moore et al. (2020)'s^[4] phylogenetic analysis to determine the relationships of Rhomaleopakhus. They found it to be a mamenchisaurid sister to Chuanjiesaurus, in a clade that also includes Analong. Their cladogram is shown below:^[1]