A Finding of Mollusks Watsonella crosbyi Grabau (Gastropoda: Helcionelliformes) in the Botomian of China

Abstract

The mollusk species Watsonella crosbyi Grabau, 1900 was found among other mollusks in the Lower Botomian strata of the Xinji Formation on the Northern China Platform (Shaanxi Province). Taxonomically the mollusk assemblage is extremely similar to that from the Mernmerna Formation, Parara Limestone, and Sellick Hill Formation of Southern Australia, the Bastion Formation of Laurentia, and the uppermost Emyaksin Formation of the Siberian Platform. All these strata can be aged as Early Botomian. The new finding of Watsonella crosbyi confirms the significant time range of the species distribution (Tommotian–Botomian) and raises doubts about newly proposed correlations of the Lower Cambrian of Southern Australia making the previously determined age of the formations one or even two ages older.