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New hadrosaurid dinosaurs from the uppermost Cretaceous of northeatern China
Several hundred disarticulated dinosaur bones have been recovered from a large quarry at Wulaga (Heilongjiang Province, China), in the Upper Cretaceous (Maastrichtian) Yuliangze Formation. The Wulaga quarry can be regarded as a monodominant bonebed: more than 80% of the bones belong to a new lambeosaurine hadrosaurid, Sahaliyania elunchunorum gen. et sp. nov. This taxon is characterised by long and slender paroccipital processes, a prominent lateral depression on the dorsal surface of the frontal, a quadratojugal notch that is displaced ventrally on the quadrate, and a prepubic blade that is asymmetrically expanded, with an important emphasis to the dorsal side. Phylogenetic analysis shows that Sahaliyania is a derived lambeosaurine that forms a monophyletic group with the corythosaur and parasauroloph clades. Nevertheless, the exact position of Sahaliyania within this clade cannot be resolved on the basis of the available material. Besides Sahaliyania, other isolated bones display a typical hadrosaurine morphology and are referred to Wulagasaurus dongi gen. et sp. nov., a new taxon characterised by the maxilla pierced by a single foramen below the jugal process, a very slender dentary not pierced by foramina, and by the deltopectoral crest (on the humerus) oriented cranially. Phylogenetic analysis indicates that Wulagasaurus is the most basal hadrosaurine known to date. Phylogeo− graphic data suggests that the hadrosaurines, and thus all hadrosaurids, are of Asian origin, which implies a relatively long ghost lineage of approximately 13 million years for basal hadrosaurines in Asia.
A. The hadrosaurid dinosaur Sahaliyania elunchunorum gen. et sp. nov., holotype GMH W453 from the Upper Cretaceous Yuliangze Formation at the Wulaga quarry, China. B. Hypacrosaurus altispinus Brown, 1913, specimen AMNH 5248 from the Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada. Braincases in dorsal (A1, A2) and left lateral (A3, A4) views; photographs (A1, A3) and explanatory drawings (A2, A4), with close−ups of the frontal region in S. elunchunorum (A5) and H. altispinus (B). Dotted lines indicate hypothetical sutures. The hadrosaurid dinosaur Wulagasaurus dongi gen. et sp. nov. from the Upper Cretaceous Yuliangze Formation at the Wulaga quarry, China. A. GMHWJ1, braincase in left (A1, A2) and right lateral (A3, A4) views; photographs (A1, A3) and explanatory drawings (A2, A4). B. GMH W421, braincase in right lateral (B1) and dorsal (B2) views.