中国东北马斯特里赫特阶的Wulagasaurus dongi(鸭嘴龙亚科)的重新评估与系统发育分析(英文)

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

通过对黑龙江省乌拉嘎地区晚白垩世渔亮子组地层发现的董氏乌拉嘎龙(Wulagasaurus dongi)的原有材料和新材料进行对比研究和重新评估,可以认定以前归入乌拉嘎龙的部分骨骼(包括不完整的脑颅骨、上颌骨和肩胛骨)实际上应该属于赖氏龙类,并相应地修订了其鉴定特征。乌拉嘎龙具有同北美地区发现的短冠龙和慈母龙十分相似的骨学特征:长而楔形的前顶点位于颧骨前支的一半背腹高度处;颧骨后支呈扇形;乌喙骨的腹突相对较长且纤细;肱骨三角胸嵴较不发育,适度地向前外方扩展;髂骨髋臼上突的腹缘呈不对称的U形,缺乏一条强烈的嵴连接其后部区域与髋臼后突的背缘。系统发育分析结果显示乌拉嘎龙、短冠龙和慈母龙共同构成了鸭嘴龙亚科的一个基干支系。该支系起源于桑托期的亚洲,可能在中坎帕期之前发生分异并通过白令陆桥向北美地区迁徙辐射。

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.