Early Cretaceous non-marine gastropods from the Xiazhuang Formation in North China

Thirteen species of non-marine gastropods recovered from the Xiazhuang Formation near Xishan, to the west of Beijing, are described. They are attributable to ten genera: Aplexa, Bithynia, Gyraulus, Lymnaea, Mesocochliopa, Mesochilina, Physa, Proauricula, Pseudarinia, and Zaptychius. Four of the species are new: Bithynia xishanensis, Mesochilina? xiazhuangensis, Proauricula elegans and Zaptychius costatus. The composition of the assemblage is consistent with an Aptian–Albian age determination. The fauna consists entirely of small specimens (none exceeds 7 mm in height) and is numerically dominated by Mesocochliopa, Pseudarinia and Zaptychius. It is inferred from this and lithological associations that the fauna probably inhabited shallow lacustrine and/or lake margin environments.