The Discovery Of Cretaceous Dinosaur Teeth From Sunjiawan Formation In Liaoning, China

This article presents the dinosaur teeth from the Sunjiawan Formation in Beipiao, Liaoning Province, China. This stratum was deposited in the Middle Cretaceous. Through the preliminary study, these specimens could be put in the group of Iguandontian, Sauropod and Theropod, respectively. It is remarkable that the theropod was found from the Sunjiawan Formation for the first time, this tooth may belong to a new genue. These discoveries enrich the dinosaur group of Sunjiawan Formation, and enhance understanding of the dinosaur in this area.The teeth of Iguandontian: All of their crown are seriously abrased, no denticle is preserved, just keep the basal part of the crown. These teeth may belong to the naturally lost teeth. The crown is wide, with development a prominent primary ridge; no serration present on the margin of the base; the wear facet is diamond, with primary ridge and weakly ridge. The tooth of Titanosauria; The top of the crown preserved. The tooth is column-shaped. The wear facet locates at the tip of the crown, similar as other Titanosauria. The cross section is D-shaped, with a weak ridge on the labial surface. The tooth of Theropod: Part of the crown preserved, near the base. The tooth is large, 16.5mm in anteroposterior length. The cross section is oval, with a ratio between the longth and width at 1.8. The crown is wide at anterior margin and thin at posterior. The serration preserved on the posterior margin. The serration is closely appressed, there is 13-14 serration per 5mm.These teeth, especially the teeth of Iguandontian and Titanosauria, are corresponding to the former reports of dinosaur fossil. They may be classified as Shuangmiaosaurus and Borealosaurus; and thses teeth give a strong support to the judgement that Shuangmiaosaurus belongs to the Iguandontian. As the first time that Theropod has been found from Sun Jiawan Formation, this tooth may stand for a huge carnivorous dinosaur, further enriching the constitute of dinosaur fauna of Sun Jiawan Formation.