Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 4e): GS12169, CH/f477, Pukekio, near Waitangi, Chatham Island, Waipawan (GNS)
(Pl. 4f): GS12169, CH/f477, Pukekio, near Waitangi, Chatham Island, Waipawan (GNS) (sculpture enlarged).
Beu & Maxwell (1990): Chapter 6; p. 90; pl. 4 e, f.
Synonymy: Chlamys mercuria Marwick 1928, p. 457
Description: Small for genus (height 12-20 mm), higher than long, apical angle acute, right valve more inflated than left. Anterior ears considerably larger than posterior ones, dorsal margins colinear; byssal notch well defined. Radial sculpture on disc of 22-24 prominent convex or subtriangular-sectioned costae. Surface apparently originally covered with rasp-like ("shagreen") microsculpture of diagonally intersecting lamellae producing a cellular pattern, but preserved only in intercostal spaces in most specimens. Anterior ears with a few weak radial costae.
Comparison: This distinctive little pecten is readily distinguished from other New Zealand species of "Chlamys" (sensu lato) by its small size, acute apical angle, strongly inflated right valve, very unequal ears, simple radial sculpture (i.e. without secondary costae) and rasp-like (shagreen) microsculpture. Shagreen microsculpture is a character limited to primitive Chlamydini (Waller 1991, 2006) and the only other taxa bearing it in New Zealand are Austrohinnites species (see below), Athlopecten athleta (Zittel, 1864) (see below), and a few other species of small, unnamed, weakly inflated scallops resembling Semipallium in the Red Bluff Tuff of Pitt Island (Beu, research in progress). "Chlamys" mercuria possibly could be related to the little-known ancestry of Austohinnites, as it resembles "Chlamys stage" juvenile specimens of Austrohinnites, before the shells become cemented to rocks.
Distribution: Waipawan, sea-cliffs near radio station, Waitangi (type) (common); Pukekio, Chatham Island (common); south coast of Chatham Island south of "the Horns"; Waihere Bay, Pitt Island; Tarawhenua Peninsula, Pitt Island (rare). All localities in the Red Bluff Tuff, Chatham Islands.
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)