RE-EVALUATION AND PHYLOGENETIC ANALYSIS OF Wulagasaurus dongi, A HADROSAURINE DINOSAUR FROM THE MAASTRICHTIAN OF NORTHEAST CHINA

XING Hai, Albert PRIETO-MáRQUEZ, GU Wei, YU Ting-Xiang

Abstract  The diagnosis of the hadrosaurine Wulagasaurus dongi is revised in this paper, based on both original and new material recovered from the Upper Cretaceous Yuliangzi Formation at the Wulaga locality in Heilongjiang Province, China. However, we also demonstrate that some specimens previously referred to W. dongi, including braincases, maxillae and scapulae, actually belong to typical lambeosaurines. Wulagasaurus shares strong morphological similarities with the North American taxa Brachylophosaurus and Maiasaura: a long, wedge-shaped rostral apex positioned at the level of the dorsoventral midpoint of the jugal rostral ramus; a fan-shaped caudal ramus of the jugal with a nearly straight or slightly convex caudal margin; a relatively elongate and slender ventral process of the coracoid; a weakly developed humeral deltopectoral crest that is moderately expanded craniolaterally; and an asymmetrical, strongly convex margin of the iliac supracetabular process, lacking a strong ridge connecting its caudal portion with the dorsal margin of the postacetabular process. Phylogenetic analysis indicates that Wulagasaurus, Brachylophosaurus and Maiasaura form a monophyletic basal clade of hadrosaurines. This basal clade originated in Asia during the Santonian age of the Late Cretaceous. No later than the middle Campanian, the lineage split and then dispersed via the Bering land bridge to North America, where Brachylophosaurus and Maiasaura diverged from one another.

Key words  Late Cretaceous, Hadrosaurinae, Wulagasaurus, basal taxon