Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
| | Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990) |
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  (Pl. 42n): GS 10849, V20/f8572, Devil's Elbow mudstone, top of north face of Devil's Elbow hill, Napier-Wairoa highway, Nukumaruan (GNS) |
Beu & Maxwell (1990): Chapter 15; p. 325; pl. 42 n.
Synonymy: Alcithoe brevis Marwick 1926a, p. 299; A. subgracilis Marwick 1926a, p. 300; A. mackayi Marwick 1926a, p. 300; Leporemax brevis; Alcithoe (Leporemax) brevis, Beu & Maxwell 1990, p. 325, pl. 42n.
Classification: Volutidae: Zidoninae
Description: Small for genus (45-80 mm high), with moderately short to very tall spire, long last whorl, deeply concave sutural ramp and (on most specimens) sharply angled shoulder. Sculpture of prominent, narrow-crested, concave-sided axial costae, extending full height of spire whorls and 0.5-0.7 of last whorl of many smaller specimens, but shorter to obsolete on last whorl of some large shells. Aperture long and parallel- sided, with thickened outer lip, 4 prominent columellar plaits, and wide, moderately deep anterior notch that forms low but obvious fasciole margined by low, very narrow ridge. Protoconch relatively large, of 2 smooth whorls, dome- shaped with an almost flat apex.
Comparison: Alcithoe brevis is highly variable in width, inflation, spire height, and prominence of axial costae. Some variants have received names; illustrated (Pl. 42n) is the subgracilis form; smaller specimens with short spires are "typical" A. brevis; and specimens with very tall spires are A. mackayi; but (as shown by the protoconch, and known in the modern species) all Alcithoe species have direct development and so can be expected to be highly varied, and the named forms intergrade. The apparently ancestral species A. gatesi (Opoitian-Waipipian; Pl. 37o) has more consistent, more even, more narrowly crested axial costae, and the succeeding species A. fusus (Castlecliffian-Recent; Pl. 49i) has weaker costae. The synonymising of Leporemax with Alcithoe is discussed under A. lepida (Pl. 21t).
Distribution: Mangapanian-Nukumaruan; Castlepoint, east Wairarapa coast, early Nukumaruan (type of A. brevis); "clays below limestone, Petane", i.e., hillside north of Petane Pa, north of mouth of Esk River, central Hawke's Bay, mid-Nukumaruan (type of A. subgracilis); "Shrimpton's", i.e., Kikowhero Stream, Matapiro Station, north of Ngaruroro River, central Hawke's Bay, late Nukumaruan (type of A. mackayi); common in shallow to moderately deep-water sandstone and mudstone throughout New Zealand.
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)