A classical taxonomic revision of Seraphsidae Gray, 1853 (Gastropoda) using a pluralist approach to species assessment

Abstract

The use of classical taxonomy, with its reliance on the physically observable, is currently waning in the face of increased reliance on molecular phylogenetics. This thesis demonstrates that a pluralistic approach to classical taxonomic practice can lead to increased internal cladistic resolution within a clade, including the recognition of new taxa at all nomenclatural levels. In particular, this thesis has three aims to bring greater resolution to the clade Stromboidea Rafinesque, 1815 (Gastropoda Linne, 1758): 1) to divide the Stromboidea into two distinctive evolutionary crown clades using morphological evidence, thereby reinstating the historical understanding of the internal cladistic relationships that have been lost as a consequence of taxonomic inflation; 2) to complete an α-taxonomic revision of Seraphsidae Gray, 1853 (Stromboidea) based on a pluralist approach to species conception; and 3) to resolve the infrafamilial relationships within Seraphsidae using morphological cladistics. This thesis examined all species hypotheses and their synonymies, and revised these in a pluralist light against the rules that govern precedence and availability. From this information, an annotated synonymy was generated for each taxon, the precedence of names determined, and revised descriptions formulated. Character sets that reflect the synapomorphies within the major subclades of Seraphsidae were coded and a cladogram generated using maximum likelihood within the tnt program with default settings. Four forms of material and evidence were used in this systematic review: 1) the type material for each taxon; 2) physical material; 3) published images; and 4) literary references for specimen localities without illustration. The current morphologically-based classification of Seraphsidae was found to be sound in terms of current species delimitations. Regardless of this, the use of a pluralist approach improved understanding of the internal cladistic relationships within Seraphsidae, which led to higher resolution of the internal cladistic arrangements and taxonomic delimitation. Furthermore, this increased resolution is now reflected in the higher evolutionary contextualisation of the family nomenclature. This thesis included Mauryna de Gregorio, 1880 within Seraphsidae on the grounds that it provides a basal link to the Seraphsidae sister taxa Semiterebellum Cossmann, 1889 and Terebellopsis Leymerie, 1846, both contained within Rostellariidae Gabb, 1868, and all three clades may in time be brought together under one family. It was not possible within the context of this thesis to test the results of the pluralist α-taxonomic findings against phylogenies generated with molecular data. This was due to the high number of extinct taxa within the Seraphsidae. Therefore, it is imperative that further revisions be undertaken with groups of predominantly extant taxa to test the pluralist classical taxonomic methodologies against molecular data, and thereby seek to reverse the trend in the literature whereby classical taxonomy is deemed fundamentally redundant in the face of advances in analysis of molecular data.