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| Qianjiangsaurus changshengi Dai, Ma, Xiong, Lin, Zeng, Tan, Wang, Zhang & Xing, 2025 |
Abstract
A non-hadrosaurid hadrosauroid, Qianjiangsaurus changshengi gen. et sp. nov., is named and described here based on an incomplete, partially articulated skeleton from the top of the Upper Cretaceous Zhengyang Formation in Qianjiang District, Chongqing Municipality, southwest China. The skeleton displays a transitional morphology between non-hadrosaurid hadrosauroids and hadrosaurids. The diagnosis of the taxon is therefore defined as a unique combination of characters, including a series of plesiomorphic features typical of non-hadrosaurid hadrosauroids, some apomorphic features common among hadrosaurids but rarely reported in non-hadrosaurid hadrosauroids, and a probable autopomorphy, namely the fan-shaped prepubic process of the pubis strongly anteroposteriorly constricted and dorsoventrally expanded, with the length/height ratio of ∼0.79. Phylogenetic analysis recovers a sister-taxon relationship between Qianjiangsaurus and Plesiohadros outside of Hadrosauridae, and the clade consisting of the two taxa is positioned higher on the tree than Gobihadros and Gilmoreosaurus, but below the clade of Telmatosaurus + Tethyshadros, Eotrachodon and Zhanghenglong. Combining the morphological data with the phylogenetic topology identifies Q. changshengi as a late-branching non-hadrosaurid hadrosauroid. Given that the age assemblage of the eight hadrosauroids closely related to Qianjiangsaurus in phylogeny spans the Santonian–early Maastrichtian time interval, the top of the Zhengyang Formation, from which Qianjiangsaurus is recovered, is possibly restricted to the late Late Cretaceous in age. Hierarchical clustering of twelve hadrosauroid-bearing dinosaur assemblages from the Late Cretaceous deposits of Asia shows a strong correlation between the Zhengyang Formation and the Djadokhta and Baruungoyot formations in Mongolia that supports coeval interchange of dinosaur faunas across East Asia.
Systematic paleontology
Dinosauria Owen, 1842
Ornithischia Seeley, 1888
Iguanodontia Dollo, 1888 sensu Sereno, 1998
Ankylopollexia Sereno, 1986 sensu Sereno, 1998
Hadrosauriformes Sereno, 1997 sensu Sereno, 1998
Hadrosauroidea Cope, 1869 sensu Sereno, 1998
Qianjiangsaurus gen. nov.
Qianjiangsaurus changshengi sp. nov.
Holotype. CLGRP V00016, an incomplete, partially articulated skeleton,
Taxonomic status of Qianjiangsaurus changshengi:
Qianjiangsaurus changshengi entirely represented by the holotype CLGRP V00016 displays a series of plesiomorphic features that are typical of non-hadrosaurid hadrosauroids, including the transversely wide, U-shaped predentary in dorsal view with the smoothly arcuate anterolateral margins, the dentary with no more than 30 alveoli, the right-angled coronoid process relative to the dorsal edge of the main body of the dentary, the dentary tooth crown lingually ornamented with a slightly distally ...
Conclusions:
Qianjiangsaurus changshengi gen. et sp. nov. is a second formally named hadrosauroid dinosaur from south China, in addition to Nanningosaurus dashiensis. The discovery of this new taxon has furthered our understanding of the diversity and late evolution of non-hadrosaurid hadrosauroids. The holotype of Q. changshengi recovered from the Upper Cretaceous Zhengyang Formation of southeast Chongqing Municipality in southwest China clearly exhibits a transitional morphology between non-hadrosaurid ...
Hui Dai, Qingyu Ma, Can Xiong, Yu Lin, Hui Zeng, Chao Tan, Jun Wang, Yuguang Zhang and Hai Xing. 2024. A New late-diverging non-hadrosaurid hadrosauroid (Dinosauria: Ornithopoda) from southwest China: Support for Interchange of Dinosaur Faunas across East Asia during the Late Cretaceous. Cretaceous Research. In Press, 105995. DOI: doi.org/10.1016/j.cretres.2024.105995
