Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 15m): GS9805, F44/f9501, Coal Brook Station, Wendon Valley, Southland, Duntroonian (GNS)
Beu & Maxwell (1990): Chapter 10; p. 160; pl. 15 m.
Classification: Volutidae: Zidoninae
Description: Size moderate for subfamily (height c.105 mm), broadly fusiform, spire 0.4 total height. Protoconch not known. Teleoconch of about 7 whorls, early whorls lightly convex, last 2 whorls becoming increasingly more strongly angled at or above middle on spire; last whorl feebly excavated below angulation, elongate. Axial sculpture on early whorls of narrow, slightly prosocline costellae reaching from suture to suture, on later whorls becoming obsolete on upper part of ramp and tubercular on shoulder angle; last whorl with 7-9 prominent, rounded costae with broad interspaces, those near outer lip less elongated axially than remainder. No spiral sculpture. Aperture large, inner lip almost straight with a thin callus smear extending some distance laterally; columella with 5 moderately prominent, subequal plaits and, on 1 shell, a 6th much weaker one above. Anterior notch deep; fasciole almost flush with whorl- surface or slightly depressed. Outer lip thin, slightly flared.
Comparison: In the absence of the protoconch the generic location of this species must be rather uncertain, but the nature of the axial sculpture, particularly the development of tubercles on the shoulder angle, and the deep anterior notch suggest that it belongs in Alcithoe rather than Spinomelon. It has some resemblance to the highly variable A. turrita (Otaian-Altonian; Pl. 21s) and may be conspecific, although all other records of A. turrita are younger and from deeper-water facies than Wendon and Chatton. These Duntroonian records are included because they seem likely to represent the oldest known member of the most characteristic genus of volutes in the New Zealand Neogene.
Distribution: Duntroonian; Chatton Formation, Wendon Valley; Shell Gully, Chatton (rare).
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
(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)