A find of mollusks Watsonella crosbyi Grabau (Gastropoda: Helcionelliformes) in the Botomian of China

Abstract

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