GNS Science

Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)

New Zealand Cenozoic Mollusca

Margineulima christyi (Marwick, 1924)


(Pl. 41h): holotype, GS1089, V21/f8482, Okauawa Stream, Kereru Road, central Hawke's Bay, Nukumaruan (TM6834, GNS)

Beu & Maxwell (1990): Chapter 15; p. 328; pl. 41 h.

Synonymy: Eulima christyi Marwick 1924c, p. 195; Margineulima christyi, Maxwell 1992, p. 120.

Classification: Eulimidae

Description: Very large for New Zealand fossil members of the family (17-18 mm high); smooth and polished, with straight sides (or, in a few specimens, lightly curved early whorls), very tall, narrow spire, and evenly rounded base. Protoconch very small and narrow, but damaged in all material seen. Aperture with weakly sigmoidal outer lip and lightly thickened inner lip; the only sculpture is faint, low, sigmoidal traces of former outer lips, randomly situated up spire.

Comparison: The generic classification of the smooth, tall and narrow, rather featureless, obligate ectoparasites of the Eulimidae has always been very difficult. Warén (1984) and Bouchet & Warén (1986) have shown that some progress can be made with meaningful subdivision of this huge group of very similar shells if the anatomy and host are known (most species are ectoparasitic on echinoderms). As these are not known for most New Zealand species and can never be known for fossil species, Beu & Maxwell (1990) adopted a rather arbitrary classification — the larger, more thick-shelled, non-umbilicate species, most of which have a straight spire, were included in Eulima (in the broad sense), whereas most of the smaller, thin-shelled non-umbilicate species, most of which have a curved or twisted spire, were included in Melanella Bowdich, 1822 (which Warén has shown is an earlier synonym for Balcis Leach in Gray, 1847). One species, however, is included in Fusceulima Laseron, 1955, another in Hypermastus Pilsbry, 1899; umbilicate species are retained in Niso Risso, 1826. This classification is not intended to imply any precision or finality. Maxwell (1992) reclassified some species, and pointed out that the unusually large species, E. christyi, E. waihaoensis Allan, 1926 (Kaiatan, McCulloch's Bridge, South Canterbury; Pl. 7s) and E. otaioensis Laws, 1933 (Otaian, Bluecliffs, South Canterbury) seem appropriately placed in Margineulima Cossmann, 1888 (type species: Eulima fallax Deshayes, 1862, Middle Eocene, Paris Basin, France).

Distribution: Nukumaruan-Castlecliffian; Okauawa Stream, Kereru Road, inland central Hawke's Bay, Nukumaruan (type); uncommon in shellbeds and near-shore mudstone in central Hawke's Bay; a few records by Fleming (1953) from Castlecliffian rocks in Wanganui basin. Other late Cenozoic species assigned to Eulima are all much smaller (4-8 mm high).

Cite this publication as: "A.G. Beu and J.I. Raine (2009). Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990). GNS Science miscellaneous series no. 27."
© GNS Science, 2009
ISBN 978-0-478-19705-1
ISSN 1177-2441
(Included with a PDF facsimile file copy of New Zealand Geological Survey Paleontological Bulletin 58 in CD version from: Publications Officer, GNS Science, P.O. Box 30368 Lower Hutt, New Zealand)


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