Forty years since Boucot, Johnson and Staton's seminal paper “On some atrypoid, retzioid, and athyridoid Brachiopoda”

Abstract

The rate at which new spire-bearing brachiopods, exclusive of spiriferids, have been described, their temporal and geographic diversity, and their grade of endemism through time are reviewed. There has been an almost four-fold increase in the number of spire-bearing brachiopod genera (spiriferids excluded) included in the revised edition of the Treatise compared with those recognized in the first edition. Many of these genera were based on specimens from previously poorly known geologic successions, especially in Russia and China where Chinese and Russian colleagues had undertaken admirable and hard research. Even assuming a relatively high proportion of invalid or synonymous genera, the annual rate of creation of genera has been five to seven times that prior to publication of the first edition. Spire-bearing brachiopod genera erected after the first edition of the Treatise show a greater degree of endemicity than those erected prior to its appearance, with endemism displayed by the athyridids being greater than for the atrypids. No correlation seems to exist between degree of endemicity and generic diversity at any specific time. Endemic spire-bearers are of great value in discriminating biogeographic units. Spire-bearing genera with cosmopolitan tendencies did not evolve rapidly, so their value for global stratigraphic correlations is generally poor. The large increase in generic-level taxa appears to have resulted in a cascading expansion in numbers of higher taxa. In addition to the remarkable increase in the number of taxa during the last four decades, there has been an obvious shift in brachiopod research with increasing integration of other disciplines (biological, palaeontologic, mineralogic), which is improving our understanding of spire-bearers, and of the phylum as a whole in time and space.