GNS Science

Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)

New Zealand Cenozoic Mollusca

Haurokoa marwicki (Finlay, 1924)


(Pl. 7u): GS9481, J41/f8025, Lorne, Kaiatan (GNS)

Beu & Maxwell (1990): Chapter 8; p. 120; pl. 7 u.

Synonymy: Cymatium marwicki Finlay 1924b, p. 456; C. sculpturatum Finlay 1924b, p. 458; Austrosassia reticulata (in part) of Finlay 1931a, p. 10 (not Streptosiphon reticulatum Suter, 1917 (Trichotropidae)); Mayena sculpturata; Austrosassia marwicki; Sassia (Haurokoa) marwicki, Beu & Maxwell 1990, p. 120

Classification: Ranellidae: Cymatiinae

Description: Small (height 25-35 mm), tall and very narrow for genus, more like Sassia in shape than are all later congeners. Protoconch relatively large (2.5-3 mm in diameter), turbiniform, of about 3 smooth whorls (complete specimens not known). Teleoconch whorls evenly convex and little-inflated on spire, last whorl tapering rapidly to a narrow neck. Axial sculpture of many low, narrow, closely spaced costae with fine threads in interspaces, and prominent, narrow varices at each 0.67 whorl down whole teleoconch. Spiral sculpture of prominent, narrow, widely spaced cords, 3 on spire whorls and 7 on sides of last whorl, with several finer ones on sutural ramp and on neck and canal, as well as fine threads in between cords. Cords forming prominent rounded nodules at intersections with costae (but not on varices), so main sculptural effect is rows of small, evenly spaced nodules; interspaces finely reticulate. Aperture oval with a short, straight siphonal canal without obvious fasciole. Inner lip narrow, thinly callused in parietal area but with thick, raised edge over lower columella; 1 large parietal ridge and 5 ridges on lower columellar area. Outer lip narrowly flared over terminal varix, with well raised rim, bearing 8 small ridges on inner edge.

Comparison: The relatively large protoconch, the straight inner lip with a raised rim, the flaring of the outer lip over the terminal varix and, in particular, the sculpture of rows of small rounded nodules indicate that Haurokoa marwicki is closely related (and possibly ancestral) to H. woodi (PI. 30b), and is the earliest species we are aware of in the genus Haurokoa. Its narrow shape and turbiniform protoconch indicate an origin from Sassia, apparently in the Australasian region, during the Paleocene or Eocene. The holotype of C. marwicki is a small but nicely preserved shell which is still the only specimen collected from McCulloch's Bridge. The holotype and seven paratypes of C. sculpturatum were reputedly from "Kakanui Beach (tuffs below limestone)" (i.e. from the Deborah Volcanic Formation (Whaingaroan) near Everett's Quarry or Gee's Point), but Maxwell (1968) showed that they (and several other species described by Finlay) are almost certainly from the green tuff (Waiareka Volcanic Formation) at Lorne, near Oamaru. H. marwicki is not uncommon at Lorne.

The most nearly similar species is a small, narrow, still more finely sculptured, unnamed one occurring in Late Eocene rocks west of Cape Otway, Victoria, Australia. To our knowledge, the genus Haurokoa is limited to Eocene to basal Pliocene rocks of New Zealand and southeastern Australia, although a poorly preserved specimen from late Miocene rocks of southern Chile, shown to us recently by Sven Nielsen (Christian-Albrechts-Universität Kiel), posssibly belongs here. The short, wide, inflated species assigned to Haurokoa differ from Sassia species strongly enough to be ranked as a separate genus.

Distribution: Kaiatan; Waihao Greensand, McCulloch's Bridge (type of C. marwicki); Waiareka Volcanic Formation, Lorne (type of C. sculpturatum).

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)


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