A New Oviraptorid (Dinosauria:Theropoda) From The Upper Cretaceous Of Nankang City, Jiangxi Province

Oviraptorosaurs are generally regarded as a group of non-avian theropod dinosaurs. They are charcterisized by short, narrow and high skulls and postcranial skeletons are mainly disitingushed by pneumatized caudal vertebra fenestra, ilia close dorsally, anteriorly concave pubic shaft, and posteriorly curved ischium. Derived forms do not bear teeth in both the upper and lower jaws, however, teeth are presented in primitive forms such as Caudipteryx zoui, Incisivosaurus gauthieri and Ningyuannia wangi. Until now, oviraptorosaurs are mainly distributed in Mongolia, China and North America. The discovered oviraptorosaurs show that they mainly come from the Cretaceous, especially the Upper Cretaceous. Oviraptorosauria can be divided into Oviraptoridae (including eighten genera), Caenagnathudae (five genera) and Caudipterygidae (two genera and three species) and some basal forms (including two genera). There are fourtheen genera of Oviraptorosauria discovered in China and they mainly belong to Oviraptoridae, Caudipterygidae and basal forms.From1960s, there are some reports about Sauropoda dinosaurs and dinosaur eggs from southeastern China, but few researches on theropoda. Until2000s, the report of Heyuannia huangi from Henyuan Basin of Guangdong Province attracts paleontologists to pay an attention to theropoda reaseaches in South China. The new specimen is discovered in the Upper Cretaceous Nanxiong Formation of the Ganzhou Basin, southern of Jiangxi Province. The new taxon adds new evidence about oviraptorosaurs’ diversity and evolution. Also, it provides much information on theropoda reaseach in Southern China.The new oviraptorid:Jiangxisaurus ganzhouensis gen. et sp. nov., is a small non-avian theropod dinosaur which was collected from the Upper Cretaceous Nanxiong Formation of Ganzhou Basin, Jiangxi Province, China. Its detailed osteological description and phylogenetic analysis are carried out. It shares the following characters with other oviraptorids:postorbital process of jugal almost perpendicular to quadratojugal ramus of jugal; the extent of deltopectoral crest (measured from humeral head to apex) about50%of the humerus length; the ratio of length of metacarpal Ⅰ to length of metacarpal Ⅱ more than0.5, rearching almost0.67; metacarpal I expanded ventrally to cover ventral surface of metacarpal Ⅱ. The autapomorphies of Jiangxisaurus ganzhouensis gen. et sp. nov. include:the dentary symphysis portion only weakly downturned; the clearly co-ossification of articular with surangular; the anteroposteriorly elongate groove on the lateral surface of surangular, with a small opening in the groove; the length ratio of radius to humerus is about0.71.In order to explore the phylogenetic position of Jiangxisaurus gen. nov. among Oviraptorosauria, phylogenetic analysis is carried out using the Branch-and-bound search method, based on21taxa (including Jiangxisaurus gen. nov.) and182characters (Osmolska et al.,2004, Longrich et al.,2010; Lii et al.,2013). The result shows that Jiangxisaurus gen. nov. falls within the rang of basal taxa, which is closely related to Gigantoraptor and Yulong. The analysis also supports Oviraptoridae as a monophyletic group same as the former studies.