GNS Science

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

New Zealand Cenozoic Mollusca

Nemocardium (Varicardium) patulum (Hutton, 1873)


(Pl. 19b): GS10365, D45/f8598, Long Beach Shellbed, Clifden, Altonian (GNS)


(Pl. 19i): GS10365, D45/f8598, Long Beach Shellbed, Clifden, Altonian (GNS)

Beu & Maxwell (1990): Chapter 11; p. 186; pl. 19 b,i.

Synonymy: Cardium patulum Hutton 1873b, p. 23; Protocardia (Nemocardium) alata Suter 1917, p. 78; Protocardia patula; Nemocardium patulum; Varicardium patulum

Type species of Varicardium Marwick, 1944

Classification: Cardiidae: Protocardiinae

Description: Moderately large for family (height 65-95 mm), robust, subequilateral, higher than long, strongly inflated; posterior area well defined, lunule not strongly differentiated. Anterior and median regions polished in well preserved shells, with commarginal sculpture of prominent rounded ridges and radial sculpture of more than 100 very fine radial lines (actually subsurface costellae that finely crenulate inner margins). Posterior area with about 30 low, rounded or flat- topped radial costae that bear minute tubercles on anterior edges on well- preserved young shells. Commarginal sculpture of growth lines that make the radial costae scaly distally. Hinge prominent, with strong anterior and posterior lateral teeth in each valve. Left hinge with prominent peg-like anterior cardinal tooth and a small posterior cardinal; right hinge with a small tubercular anterior cardinal attached to top of prominent triangular median cardinal. Adductor muscle scars large, ovate, subequal.

Comparison: The poorly known N. (Varicardium) serum (Duntroonian, Castle Hill Basin) is very similar to N. patulum, apparently differing only in its smaller size (less than 65 mm in height) and its slightly less rounded shell — it may not be distinct.

Varicardium is very similar to Nemocardium (sensu stricto) but the periostracal nodules on the posterior area characteristic of the latter taxon are smaller in Varicardium. Varicardium is recorded from Kaiatan to Waiauan in New Zealand; the only local record of Nemocardium (sensu stricto) is from the Bortonian Stage (N. carteri Maxwell, 1992, p. 75; McCulloch's Bridge). The living tropical Indo-West Pacific species Nemocardium bechei (Reeve) is very similar to N. patulum and could be referred to N. (Varicardium), but a more likely taxonomy is that Varicardium intergrades with Nemocardium in sculptural prominence.

Distribution: Waitakian(?); Otaian-Waiauan; The Deans", Waipara (type locality of C. patulum — probably Mount Brown Formation, Weka Creek, Altonian?); Neothyris Shellbed, Weka Creek, Altonian (type locality of P. alata) and numerous localities throughout North and South Islands, where it is the most characteristic cardiid in shallow-water assemblages.

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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