Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 44m, n): holotype of Lima marwicki Powell, Castlecliff, Wanganui (almost certainly from Tainui Shellbed), Castlecliffian (TM4276, GNS)
Beu & Maxwell (1990): Chapter 16; p. 341; pl. 44 m, n.
Synonymy: Lima orientalis A. Adams & Reeve 1850, Mollusca p. 75; Lima (Mantellum) marwicki Powell 1926c, p. 48; Promantellum marwicki
Description: Small for family (20-28 mm high), very thin and brittle, weakly inflated, elongated obliquely postero- ventrally, with straight hinge-line, umbones projecting weakly above centre of hinge. Anterior outline moderately convex except for shallow embayment marking off small anterior ear; ventral margin strongly convex; postero-dorsal margin long, straight except for very slight embayment below hinge line. External sculpture of many very narrow, relatively widely spaced radial costae, most prominent on postero-dorsal slope, but absent from postero-dorsal area and anterior ear; rendered finely scaly by commarginal growth lamellae. Hinge narrow, smooth except for wide, shallow, central triangular resilial pit. Interior apparently smooth and shiny, without visible characters.
Comparison: Limaria orientalis is easily recognised by its oblique, trigonal shape and its very thin, finely sculptured shell. It occurs in the modern fauna from Japan, throughout the western Pacific to New South Wales, Victoria and South Australia, and Willan (1973), Grange (1974) and Powell (1974) discussed its abrupt appearance in the north-eastern North Island during 1972. Since then it has become a normal, common member of the fauna, most commonly found nestling in algae or under boulders in the intertidal zone of the muddy outer parts of large estuaries, but also dredged commonly in 10-30 m on the inner shelf and locally in up to about 80 m, and as far south as East Cape, on coarse substrates. Hayward et al. (1986) found very high densities of specimens (up to 400 per square metre) in depths of 10-20 m off the Broken Islands, on the west side of Great Barrier Island, east of Auckland. The many occurrences since its Duntroonian (Oligocene) appearance in New Zealand were discussed by Beu (1977c); most occurrences probably reflect a continuous presence in New Zealand, but its apparent absence from New Zealand between mid-Castlecliffian time and 1972 suggests that it has arrived here again as planktonic larvae after becoming extinct during several of the many Pleistocene glaciations.
Distribution: Duntroonian(?)-Recent, but possibly discontinuously; Recent, "Philippine Archipelago" (type of Lima orientalis); Castlecliff, Wanganui, Castlecliffian (almost certainly from Tainui Shellbed) (type of Lima (Mantellum) marwicki). Common in some offshore to near-shore mudstone beds at Castlecliff, Wanganui (Castlecliffian; from oxygen isotope stage 17 onwards, only) and in central Hawke's Bay (Nukumaruan); Duntroonian to Pliocene records were listed by Beu (1977c).
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)