A new helcionelloid mollusk from the middle Cambrian Burgess Shale, Canada

Abstract

Burgess Shale-type faunas provide unique insights into the Cambrian “explosion”. Their degree of representativeness of Cambrian marine life in general is, however, less easy to establish. One line of evidence is to consider only the skeletal component of a Burgess Shale-type fauna and compare that with a typical Cambrian assemblage. This paper describes a new species of helcionelloid mollusk ( Totoralia reticulata n. sp.) from the middle Cambrian Burgess Shale of British Columbia. Whilst much rarer than the co-occurring smooth shelled helcionelloid Scenella amii , the strongly costate morphology of Totoralia reinforces comparisons with Cambrian shelly faunas. The extension of the range of Totoralia from Argentina to Canada adds support to the proposed derivation of the Precordillera terrane of Mendoza from Laurentia.