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. 21p): GS9685, J41/f9499B, Pukeuri road cutting, Oamaru, Altonian (GNS) |
Beu & Maxwell (1990): Chapter 11; p. 203; pl. 21 p.
Synonymy: Parvimitra pukeuriensis Finlay 1930b, p. 63; Proximitra (Parvimitra) pukeuriensis; Peculator (Parvimitra) pukeuriensis, Beu & Maxwell 1990, p. 203, pl. 21p; Parvimitra scopi Finlay 1930b, p. 64; Parvimitra ponsatanae Finlay 1930b, p. 64
Type species of Parvimitra Finlay, 1930, synonymised with Peculator by Maxwell (1992, p. 137).
Classification: Volutomitridae
Description: Rather small for family (height 6-9 mm), elongate-ovate to biconic, spire 0.3-0.4 total height. Protoconch mamillate, of about 1.25 smooth whorls, not sharply distinguished from teleoconch. Teleoconch of 3.5-4 whorls, typically becoming shouldered at an early stage of growth; angulation well marked in most shells — though becoming less distinct on later part of last whorl of most shells — but very weak in some shells; situated at or slightly below middle on spire whorls of most shells, but much lower in others, sutural ramp almost flat or with weak subsutural swelling. Last whorl elongate, weakly excavated, neck short. Axial sculpture highly variable, almost completely obsolete in some shells but consisting of small, rounded peripheral tubercles on most shells, typically obsolete on ramp, but extending down to lower suture on spire whorls on most shells, in many shells becoming obsolete near outer lip on last whorl; 9-22 nodules on penultimate whorl. Spiral sculpture subdued, almost completely obsolete on some shells, but more obvious on others, consisting of feeble striae that on most shells are most conspicuous on shoulder angulation or on neck. Aperture narrow, elongate; siphonal canal short, weakly differentiated; columella oblique, almost straight, with 4 plaits, the anterior one noticeably stronger than the others. Outer lip thin, smooth within.
Comparison: Peculator pukeuriensis differs from P. plicatellus (Pl. 8j) in being somewhat thicker-shelled, in typically having more strongly shouldered teleoconch whorls, and in being more weakly spirally sculptured. P. paucinoda (Otaian, Bluecliffs and Pareora River) is larger than P. pukeuriensis (height 7-12 mm), has more prominent spiral sculpture, and typically has a strongly projecting peripheral keel. Small specimens of Proximitra apicalis (see above) may be distinguished from P. pukeuriensis by the larger protoconch, the stronger spiral sculpture, and the relatively much weaker anterior columellar plait of P. apicalis.
Distribution: Altonian; Mount Harris Formation, Oamaru; Pukeuri road cutting (type locality of P. pukeuriensis); Target Gully Shellbed (type locality of P. scopi); Ardgowan Shellbed (type locality of P. ponsatanae); Awamoa Creek; Old Rifle Butts. Particularly common at Pukeuri, less so elsewhere.
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)