New oospecies of Spheroolithidae from the Upper Cretaceous in the Laiyang Basin, Shandong Province, China

Five deformed dinosaur eggs are newly discovered from the Upper Cretaceous Jiangjunding Formation in the Laiyang Basin, Shandong Province, China. A new oospecies of Spheroolithidae, Spheroolithus phacelus, was erected based on the spheroid eggs and the developed cone-shaped eggshell unit assemblages. Radial sections of S. phacelus show the inner cone-shaped eggshell units, the middle columnar eggshell units and the outer bush-like eggshell units. Numerous cone-shaped eggshell unit assemblages and large gaps between them are developed in the inner part, columnar eggshell units and small pores emerge in the middle part, and branches of eggshell units appear in the outermost part, forming bush-like microstructures. Spheroolithidae is a typical oofamily of East Asia consisting of Spheroolithus spheroides, S. chiangchiungtingensis, S. quantouensis, S. oosp. and Paraspheroolithus irenensis, which mainly distributed in the Upper Cretaceous of China, South Korea, Japan and Mongolia. The discovery of S. phacelus provides new fossil materials of oogenus Spheroolithus in Spheroolithidae and expands the palaeogeographic distribution of Spheroolithidae in East Asia, which may be eggs of hadrosauroid. The age of these deformed dinosaur eggs could be presumed to be the middle Late Cretaceous (Coniacian–Campanian).