Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 10g): GS9806, F45/f9668, Shell Gully, Chatton, Duntroonian (GNS)
(Pl. 10i): GS9806, F45/f9668, Shell Gully, Chatton, Duntroonian (GNS)
Beu & Maxwell (1990): Chapter 10; p. 146; pl. 10 g, i.
Synonymy: Venericardia christiei Marwick 1929, p. 910; V. (Megacardita) christiei; V. (Cyclocardia) christiei
Classification: Carditidae: Venericardiinae
Description: Moderately large for family (height 45-65 mm), robust, ovate, generally higher than long, with beaks close to anterior end. Posterior end only weakly truncate. Lunule very narrow, strongly impressed, sloping backwards under beak; escutcheon narrow, almost vertical. Radial sculpture of 22-24 prominent costae, typically sharply defined and somewhat flattened on top on proximal half, but lower, less distinct and more rounded distally. Costae on umbones bearing small tubercles on their crests, but soon becoming smooth or bearing only line growth lines. Left hinge with a narrow, backward-directed anterior cardinal tooth and a long, arched posterior cardinal. Right valve with a low anterior cardinal tooth confluent with lunular margin, a broadly triangular, arched median cardinal, and a thin, grooved posterior cardinal joined to nymph.
Comparison: "Cyclocardia" christiei is similar to "Cyclocardia" awamoensis (Pl. 17h, i) but is much larger, thicker-shelled and more oblique, and has more prominent radial costae. "Cyclocardia" marama (Waitakian, North Otago and South Canterbury) is smaller and more circular than "C." christiei, and has weaker radial sculpture and a nearly vertical lunular margin. Although these species were referred to Cyclocardia Conrad, 1867 by Maxwell (1969, p. 172) their resemblance to the type species of that genus is almost certainly fortuitous, and they are probably derived from a New Zealand Eocene species of Glyptoactis (Fasciculicardia). The generic position remains uncertain in 2009.
Distribution: Duntroonian; Chatton Formation, Shell Gully, Chatton (type) (abundant); Wendon Valley, Southland (abundant);? Waiwiri Beach, Southwest Auckland (very large shells up to 85 mm in height, with sculpture becoming obsolete distally).
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)