Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 45i): GS4033, R22/f6371, Lower Castlecliff Shellbed, Castlecliff, Wanganui, Castlecliffian (oxygen isotope stage 11) (GNS)
Beu & Maxwell (1990): Chapter 16; p. 334; pl. 45 i.
Synonymy: Notovola marwicki Finlay 1930b, p. 52; Pecten benedictus tepungai Fleming 1957, p. 33; Pecten benedictus marwicki, Beu & Maxwell 1990, p. 334, pl. 45i.
Description: Very large for genus, to about 130 mm high and 180 mm long, i.e., markedly longer than high in large individuals; left valve slightly and evenly concave, right valve moderately convex, with anterior and posterior ends compressed into relatively weakly convex extensions of disc. Ears almost equal. Right valve with about 15 to 18 low, wide radial costae of evenly convex section, blending into their shallow, evenly concave interspaces, each interspace only slightly narrower than 1 costa. Left valve with narrow, very low, flat-topped radial costae. Commarginal lamellae largely absent from right valve, prominent on some left valves, particularly in intercostal spaces.
Comparison: Beu (2006, pp. 194-209) reconsidered the several forms of Pecten named from New Zealand by Fleming (1957), and synonymised them all with P. novaezelandiae. The reader is referred there for a detailed discussion. The 2 extreme end-members of the variation are illustrated here, "Pecten benedictus marwicki" and "Pecten novaezelandiae tainui" of Fleming's classification, and the original descriptions by Beu & Maxwell (1990) have been retained. The P. novaezelandiae "marwicki form" is very similar to the Mediterranean Miocene and Pliocene species P. benedictus (Lamarck), and Fleming's (1957, p. 30) suggestion of a close genetic relationship between these populations appears realistic, although these "species groups" are all much more closely related than Fleming's discussion indicates. For example, several workers have suggested recently that the Atlantic "species" Pecten maximus (Linnaeus, 1758) and the Mediterranean "species" P. jacobaeus (Linnaeus, 1758) are conspecific, changing characters abruptly at an ecotone just inside the Straits of Gibralter. The form named P. tainui (below) has flat-topped radial costae with prominent, vertical (or even undercut) edges, contrasting strongly with the low, gently rounded costae of the "marwicki form", but intermediate specimens are known, and were named P. jacobaeus toi by Fleming (1957). Much of the text by Beu & Maxwell (1990) has been deleted.
Distribution: Late Castlecliffian only; Castlecliff, Wanganui, horizon not specified (type of Notovola marwicki; probably from Upper Castlecliff Shellbed - Fleming 1957, p. 30); Rangitawa "fossil beds" (Te Punga 1962), Rangitawa Stream, Rangitikei Valley (type of Pecten benedictus tepungai). This form is abundant in beds of low-energy, shallow-water facies of the late Castlecliffian (oxygen isotope stages 15 to 11 and possibly 9) in the Castlecliff and Rangitikei River sections, Wanganui basin. However, other forms alternate in rocks of other facies, and it is now clear that these are all ecological forms of a single species.
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)