New information on the Cretaceous sauropod dinosaurs of Zhejiang Province, China: impact on Laurasian titanosauriform phylogeny and biogeography

Titanosaurs were a globally distributed clade of Cretaceous sauropods. Historically regarded as a primarily Gondwanan radiation, there is a growing number of Eurasian taxa, with several putative titanosaurs contemporaneous with, or even pre-dating, the oldest known Southern Hemisphere remains. The early Late Cretaceous Jinhua Formation, in Zhejiang Province, China, has yielded two putative titanosaurs, <i>Jiangshanosaurus lixianensis</i> and <i>Dongyangosaurus sinensis</i>. Here, we provide a detailed re-description and diagnosis of <i>Jiangshanosaurus</i>, as well as new anatomical information on <i>Dongyangosaurus</i>. Previously, a 'derived' titanosaurian placement for <i>Jiangshanosaurus</i> was primarily based on the presence of procoelous anterior caudal centra. We show that this taxon had amphicoelous anterior-middle caudal centra. Its only titanosaurian synapomorphy is that the dorsal margins of the scapula and coracoid are approximately level with one another. <i>Dongyangosaurus</i> can clearly be differentiated from <i>Jiangshanosaurus</i>, and displays features that indicate a closer relationship to the titanosaur radiation. Revised scores for both taxa are incorporated into an expanded phylogenetic data matrix, comprising 124 taxa scored for 548 characters. Under equal weights parsimony, <i>Jiangshanosaurus</i> is recovered as a member of the non-titanosaurian East Asian somphospondylan clade Euhelopodidae, and <i>Dongyangosaurus</i> lies just outside of Titanosauria. However, when extended implied weighting is applied, both taxa are placed within Titanosauria. Most other 'middle' Cretaceous East Asian sauropods are probably non-titanosaurian somphospondylans, but at least <i>Xianshanosaurus</i> appears to belong to the titanosaur radiation. Our analyses also recover the Early Cretaceous European sauropod <i>Normanniasaurus genceyi</i> as a 'derived' titanosaur, clustering with Gondwanan taxa. These results provide further support for a widespread diversification of titanosaurs by at least the Early Cretaceous.