A new egg with avian egg shape from the Upper Cretaceous of Zhejiang Province, China

Abstract

A new egg is described from the Upper Cretaceous lacustrine deposit of the Chichengshan Formation in the Tiantai Basin, Zhejiang Province, southeast China. The new specimen shares eggshell micro-features with members of the oofamily Stalicoolithidae, Paraspheroolithus of the oofamily Spheroolithidae and Mosaicoolithus (oofamily indet.), with barrel-shaped cones, prolatocanaliculate pore system, horizontal accretion lines and light stripes throughout the eggshell. However, the new egg differs from the aforementioned ootaxa by its small size and asymmetrical shape, revealing new morphological variation among eggs with microstructure similar to that of Paraspheroolithus, Mosaicoolithus and Stalicoolithidae. We refer the new egg to a new oogenus and oospecies, thus increasing the diversity of the Tiantai Basin oofauna. The Tiantai Basin has yielded a variety of dinosaur eggs and one turtle clutch. Comparatively, the new egg is surprisingly small and ovoid, a morphology usually associated with avian eggs, although the absence of a squamatic layer excludes the egg from being referred to this group.

Keywords::

• Parvoblongoolithus
• avian egg shape
• Tiantai Basin
• Chichengshan Formation
• Upper Cretaceous

Acknowledgements

The authors would like to thank Z.K. Zhao for critical comments; Z.H. Zhou for useful suggestions; and K.E. Mikhailov and C.S. Sullivan for helpful discussions.

Additional information

Funding

This work was supported by the National Basic Research Program of China (973 Program, 2012CB821906), the National Natural Science Foundation of China.