Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 3a): holotype, GS1177, CH/f3, Tioriori, Chatham Island, Waipawan (TM4286, GNS)
(Pl. 3f): holotype, GS1177, CH/f3, Tioriori, Chatham Island, Waipawan (TM4286, GNS)
Beu & Maxwell (1990): Chapter 6; p. 91; pl. 3 a, f.
Synonymy: Ostrea cannoni Marwick 1928, p. 462
Classification: Gryphaeidae: Pycnodonteinae
Description: Rather small for genus (height 132 mm), subtrigonal, known definitely only by the thick-shelled but only slightly inflated left valve. Umbo subtriangular, projecting strongly above hinge. Shell apparently composed of alternating lamellar and vesicular calcite. Attachment area large. Sculpture highly irregular, of puckers and welts; some suggestion of radial folds. Ligamental area large, triangular, with prominent central resilifer. Chomata very weakly developed, adjacent to ligamental area. Adductor muscle scar suboval, slightly posterior to middle of valve.
Comparison: Crenostrea cannoni is the oldest known member of the genus, differing from C. wuellerstorfi (PI. 12a, b) in its more equilateral shape, much larger ligamental area and smaller adductor muscle scar, and in having almost obsolete chomata. Crenostrea was long thought to be endemic to New Zealand, but a species of probable Oligocene age has been described from Costa Rica (Woodring 1976).
Distribution: Waipawan ?, Tutuiri Greensand, Tioriori, north Chatham coast (rare); ?Matanginui Limestone, mouth of Waipapa Stream, Chatham.
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)