New oospecies of dinosaur eggs from the Upper Cretaceous of South Anhui

Abstract

A new oogenus and oospecies, Umbellaoolithus xiuningensis oogen. et oosp. nov., is described on the basis of specimens from the Upper Cretaceous Huizhou Formation in the Huangshan area of Anhui Province, China. The Mesozoic strata developed in South Anhui, producing a large number of dinosaur skeletons, dinosaur eggs, dinosaur footprints and so on. The Xiuning Basin is a small intermountain basin during the Mesozoic. The Triassic strata are scattered and the Jurassic and Cretaceous strata are intact in the basin. The Jurassic strata include the lower Jurassic Yuetan Formation, and Middle Jurassic Hongqin Formation. The Cretaceous strata include the lower Cretaceous Bingqiu Formation, Shiling Formation and Yantang Formation, Upper Cretaceous Huizhou Formation, Qiyunshan Formation and Xiaoyan Formation. The materials we studied were found in the Huizhou Formation of Qiyunshan, Xiuning, in 2011. There is an incomplete egg nest consisting of at least 9 dinosaur eggs. The eggs are oval, arranged along the long axis of all the eggs parallel to each other, and not at the same horizontal level within the clutch, obviously differing from the elongated eggs, paired, regular arrangement and radial orientation seen in clutches attributable to the Elongatoolithidae and Macroelongatoolithidae. The eggs of Umbellaoolithus xiuningensis also differ in typical alignment from those of the Prismatoolithidae, which are vertical or near vertical. The average diameter of the eggs is 13.86 cm, the equatorial diameter is 10.43 cm, and the shape index is 75.25. In general, the eggshell units have the shape of an umbrella, triangle or cone, and are arranged irregularly, unlike in the Spheroolithidae, Stalicoolithidae and Ovaloolithidae. The cones are hemispherical in shape. The cone layer is very thin, its average thickness of 0.12 mm representing approximately 1/6 of the total eggshell thickness. Umbrella-like eggshell units are well-developed near the inner and outer surfaces of the columnar layer. The eggshells have numerous irregular pores, unlike in several oofamilies including the Dictyoolithidae and Faveoolithidae. Consequently, we established a new oofamily: Umbellaoolithidae oofam. nov.. This new specimen unambiguously represents a distinct oospecies of dinosaur eggs in southern Anhui, and provides new paleontological evidence bearing on the classification and correlation of Upper Cretaceous strata in southern Anhui.