Taxonomy of the Late Triassic bivalve Monotis

Abstract

The scope and species content of the pterioid bivalve Monotis Bronn with almost global distribution in Norian (Late Triassic) marine strata are reconsidered. Various infra-generic groupings have been proposed in the last 50 years and all have been subject to some criticism. A scheme which allocates all species to one of eight subgenera (Monotis, Entomonotis Marwick, Eomonotis Grant-Mackie, Inflatomonotis Grant-Mackie, Maorimonotis Grant-Mackie, Pacimonotis Grant-Mackie & Silberling, Baikalomonotis Bychkov and Praemonotis Bychkov) is favoured here and, in line with current trends, these eight are afforded generic status. There is also a growing move away from recognition of subspecies and, when applied here, allows most to be accepted at species level with a few names synonymised.