The first Dictyoolithus egg clutches from the Lishui Basin, Zhejiang Province, China

Abstract

ABSTRACT Three clutches and eight additional eggs are described from the Upper Cretaceous Chichengshan Formation in the Lishui Basin of Zhejiang Province, China. The three clutches contain 6–18 partial or complete spherical eggs, 14–18 cm in diameter. The eggshell thickness and reticulate pore system are identical to Dictyoolithus hongpoensisZhao, 1994. However, the eggshell lacks superimposed shell units previously reported in this oospecies. The difference in microstructure most likely results from the reliance on thin section analysis in the original study; furthermore, superimposed shell units are inadequately documented in all Dictyoolithus oospecies due to the absence of scanning electron microscopy (SEM) or low (×45) magnification of SEM imaging. Cladistic analysis and the presence of the following characters support a theropod affinity of Dictyoolithus hongpoensis: relatively narrow spacing of nucleation sites, mammillary cones with blocky calcite cleavage, prismatic columns, and parallel laminae within the shell units. We reevaluate previous assignment of Dictyoolithus eggs to the Dinosauroid-spherulitic Basic Type and advocate discontinuation of Basic Type and Morphotype in fossil egg classification.