Abstract:
This doctoral thesis examines sponges of the order Dictyoceratida, based primarily on the study of field collections and museum specimens from New Zealand. This study has discovered and formally described in 29 new species, four new genera and two new subgenera" with the reassessment and clarification of, or amendments to, the diagnoses of eight genera, namely: Spongia, Hippospongia, Ircinia, Psammocinia, Dysidea, Cacospongia, Thorecta and Thorectandra. This process, along with a collection of overseas voucher specimens, facilitated a synoptic view of dictyoceratid genera" which provides an up-to-date foundation for the continued study of dictyoceratid systematics worldwide. Literature references to dictyoceratid sponges in New Zealand waters prior to this study are largely unreliable, and almost all of them are incorrect. This study highlights, though not for the first time, the problems associated with a lack of recognisable morphological characters used in the identification of sponges, and the relative importance of those characters in defining the taxonomic boundaries between taxa. It is believed that dictyoceratid systematics in the immediate future would be best served by clearly validating and documenting the existence of accessible, extant type material, and by establishing a widely available taxonomic database of dictyoceratid sponge species.
