Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 30e): GS4588, R13/f6583, Goldsborough-Kumara Road, Hokitika district, Westland, Kapitean (GNS)
Beu & Maxwell (1990): Chapter 13; p. 266; pl. 30 e.
Synonymy: Falsicolus coerulescens Finlay 1930e, p. 266; Austrofusus tuberculatus Marwick 1931, p. 113; Austrofusus (Austrofusus) coerulescens, Beu & Maxwell 1990, p. 266, pl. 30e.
Description: Small for genus (20-50 mm high), with moderately tall spire (equal to or slightly higher than aperture and canal), narrow, strongly concave sutural ramp but whorls otherwise strongly and evenly convex, and short, open, only weakly twisted anterior canal with low fasciole bounded by narrow ridge. Sculpture of high, narrowly crested spiral cords with interspaces a little wider than 1 cord, 3 or 4 on spire whorls and 10 (plus several finer ones on canal) on last whorl, with 1-3 fine spiral threads in each interspace; crossing many narrow, low, closely spaced axial costae, about 17-20 per whorl, forming small, sharply rounded nodules at all sculptural intersections around periphery and upper part of base; an overall impression of small, evenly spaced nodules all over an evenly convex shell. Protoconch conical, presumably as in other A. (Aethocola) species, but abraded on specimens seen.
Comparison: Aethocola coerulescens is an extremely distinctive species of uncertain origin, short time range, and abrupt extinction, and as it is easily recognised because of its evenly nodulose sculpture, and is abundant throughout New Zealand in early Kapitean rocks, it has long been regarded as one of the most important Kapitean index species (the other is Sectipecten wollastoni, Pl. 28f). However, recent studies in conjunction with micropaleontological biostratigraphy have shown that A. coerulescens disappears abruptly at the end of the Globorotalia conomiozea zone, i.e., it does not occur (and nor do any other distinctly Miocene Mollusca) in the late Kapitean Globorotalia sphericomiozea zone.
Distribution: Kapitean (early Kapitean Globorotalia conomiozea zone only); Bluecliff, Te Waewae Bay, Southland (type of Falsicolus coerulescens); coast east of mouth of Awatere River, Te Araroa, near East Cape (type of Austrofusus tuberculatus); common throughout New Zealand in early Kapitean rocks wherever shelf facies occur.
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)