P. A. Maxwell. New Zealand Geological Survey Palacontological Bulletin 55, 1988.
Originally reviewed by Walter Sage in 1989.
Published in Journal of Conchology (1989), Vol.33
This Bulletin is concerned with the molluscan faunules found at two localities about a kilometre apart on the north- west coast of South Island, New Zealand. It is of interest firstly because there have been relatively few studies of Neogene deep-water mollusc faunas and, secondly, for the taxonomic conclusions given, or foreshadowed, in it.
A comparison with selected Miocene molluscan faunules in New Zealand is followed by a balanced discussion of the evidence from the Mollusca that the Stillwater mudstone was laid down in the upper bathyal zone at a depth of probably 400-800 m. A bathymetric analysis (by genus) precedes a Taxonomic Structure Analysis which produced a result not closely corresponding to that for any present day depth zone. Reasons for the anomalies are considered with the sensible conclusions that factors other than water depth can have a significant effect on the taxonomic structure of a molluscan faunule and that Taxonomic Structure Analysis requires refinement before it can be used for paleobathymetric interpretations. The paleoecological section of the Bulletin ends with a trophic analysis of the two faunules which is thorough and decides that their preserved component is dominated by presumed deposit feeders and carnivores. There was an abundance of worm-eating molluscs, and molluscs were in turn preyed upon by other molluscs, decapod crustaceans and telcost fish.
The bivalve fauna was dominated by protobranchs and the systematic consideration of these includes a revised classification of New Zealand species assigned to Jupiteria Bellardi, 1875. The presence of Parvamussium n.sp. caused the author to review the classification of New Zealand internally costate pectens.
In dealing with the gastropods, I was glad to see the author merging the New Zealand Zexilia Finlay, 1927 with the North American and European Exilia Conrad, 1860 and giving notice of intent to publish reasons for locating the genus in the Turbinellidae. On the Turridae he proposes that the subfamily Cochlcspirinae Powcll, 1942 (= Turriculinae Powell, 1942, sensu Powell, 1966 but excluding Pseudotominae Bellardi, 1875) he synonymized with the Turrinae Swainson, 1840 because the position of the anal sinus in relation to the shell periphery cannot be sustained as a suprageneric taxonomic criterion. Mauidrillia Powell, 1942, to which a number of late Eocene to Pliocene New Zealand and Australian fossils have been assigned, is relocated in the subfamily Borsoniinae, with the suggestion that it may by a synonym of Typhlomangelia Sars, 1878; (I suggest this could be followed up by comparing the species assigned to both genera with various species allocated to Asthenotoma Harris and Burrows, 1891). A similar transfer is made for Tomopleura, Casey, 1904.1 am not sure why, in a summary of the classification of species previously assigned to Mioawateria Vella, 1954, Antiguraleus Powell, 1942 has been placed in the Raphitominae.
New taxa, new synonymies and new combinations proposed are conveniently listed on page 77. The photographs excellently illustrate the Stillwater Mudstone molluscan fauna. Typographical errors are very few indeed.
The Bulletin is thoroughly recommended for all interested in the molluscan groups where the author has made taxonomic revisions and innovations, in the ecology and paleoecology of deep-water molluscs and in the marine mollusca, living and fossil, of Australia and New Zealand. It is obtainable from the New Zealand Geological Survey, PO Box 30368, Lower Hutt, New Zealand.