Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 22k): GS12324, J41/fl98, Old Rifle Butts, Cape Wanbrow, Oamaru, Altonian (GNS)
Beu & Maxwell (1990): Chapter 11; p. 210; pl. 22 k.
Synonymy: Austrotoma nervosa Powell 1942, p. 76
Classification: Turridae: Pseudotominae
Description: Size moderate for genus (height 35-55 mm), fusiform, spire about half total height. Protoconch as in A. lawsi (see above). Teleoconch of 5-6 whorls, shouldered well above middle on spire; sutural ramp strongly concave, subsutural fold weakly developed on early whorls, obsolete on later whorls; last whorl weakly excavated. Axial sculpture, apart from growth lines, confined to first 2 or 3 whorls, consisting of narrow costae extending from shoulder angle to lower suture. Spiral sculpture of fine threads on ramp, and low, flattened cords below, 16-20 on last whorl. Spaces between cords smooth or with a single weak thread. Aperture more elongate than in A. lawsi but otherwise similar.
Comparison: The tall spire, slender shape, early obsolescence of axial costae, and relatively simple spiral sculpture effectively distinguish Austrotoma nervosa from most of its congeners. The most similar species (and its probable ancestor) is A. finlayi (Waitakian-Otaian, Auckland, North Otago), which differs in having axial costae persisting to a much later stage of growth (on to the penultimate whorl in some shells).
Distribution: Altonian; Mount Harris Formation, Mt Harris (type); Awamoa Creek; Old Rifle Butts; Dyer's Run, Waihao Valley; Ardgowan Shellbed; Mokau Formation, North Taranaki. Rather uncommon at all localities.
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)