The bivalve Ambonychia in the Ordovician of New Zealand

Abstract

A new bivalve species, Ambonychia hailesensis (Ambonychiacea: Ambonychiidae), is described from a boulder of Arthur Marble (Late Ordovician), Hailes Knob, northwest Nelson, South Island, New Zealand. The species is the first record of an Ordovician bivalve from New Zealand and the only confirmed Ambonychia presently known from Australasia. The occurrence of Ambonychia in Gondwanaland shelf seas may be explained by oceanic migration. It is suggested that although morphological affinities exist with North American and European specimens, specific differences in the New Zealand species probably resulted from isolation and consequental divergent evolution. © 1999 Taylor & Francis Group, LLC.