Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 5c): GS9959, J40/f6610, South Branch, Waihao River near "Pentland Hills", Bortonian (GNS)
(Pl. 5e): GS9959, J40/f6610, South Branch, Waihao River near "Pentland Hills", Bortonian (GNS)
Beu & Maxwell (1990): Chapter 7; p. 101; pl. 5 c, e.
Synonymy: Ostrea gudexi Suter 1917, p. 71; Lopha gudexi; Lopha pahiensis Finlay 1928b, p. 266
Classification: Ostreidae: Ostreinae
Description: Size moderate for family (height 20-70 mm), shape highly variable and irregular, but typically inequilateral, oblique. Strongly inequivalve, left flower) valve markedly inflated, some shells with rather obscure crescentic keel defining a posterior area; attachment area moderately large. Right valve typically slightly convex or almost flat, but largest specimens with pronounced submedian sulcus distally. Sculpture highly discrepant, right valve smooth except for growth ridges; left valve with prominent, irregular, bifurcating and intercalating radial costae crossed by growth ridges, typically from 7-20 costae in small or medium-sized shells (20-40 mm high) but over 25 in largest specimens (55 mm). Ligamental area small, chomata short, rather inconspicuous, confined to proximal region. Adductor muscle scar lachrymiform, posterior to middle of valve. Inner margins of right valve smooth, those of left valve coarsely crenulate.
Comparison: Cubitostrea gudexi is distinguished from other New Zealand oysters primarily by its strongly discrepant sculpture. The genus seems to have been very widespread during the Eocene, and is recorded from Europe, India, North America and Patagonia. Although it is not known after the Bortonian in New Zealand, Cubitostrea persisted until the Oligocene in Europe (Stenzel 1971, p. N1142).
Distribution: Porangan (?), Bortonian; Waihao Greensand, Kakahu, Bortonian (type of O. gudexi); Pahi Greensand, Pahi, Northland, Bortonian (type of L. pahiensis); not uncommon at several localities with shallow-water assemblages in Northland, Westland, North Otago and South Canterbury.
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)