Very old patelliform gastropods from the Early Cambrian of China: Reconsideration of the systematic position of Archaeotremaria

Abstract

-Archaeotremaria polytremata Yu from the Lower Cambrian Maidiping Member of the Hongchunping Formation of Sichuan, China, was originally described as a primitive monoplacophoran. A restudy of the holotype and paratype has led to a reconsideration of its systematic position. A. polytremata has a patelliform shell with a series of median-dorsal tremata extending from the apex to the anterior margin and periodic rugae. The species is now reassigned to the Gastropoda, rather than Monoplacophora.