Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 7g): GS9481, J41/f8025 and GS831, J41/f8467, Lorne, Kaiatan (GNS)
(Pl. 7h): GS9481, J41/f8025 and GS831, J41/f8467, Lorne, Kaiatan (GNS)
Beu & Maxwell (1990): Chapter 8; p. 114; pl. 7 g, h.
Synonymy: Glycymeris lornensis Marwick 1923, p. 66-67; G. (Grandaxinea) lornensis
Classification: Glycymerididae: Melaxinaeinae
Description: Rather small for genus (height 35-45 mm), ovate, subequilateral, posterior area slightly depressed. Radial sculpture of 34-38 prominent rounded or somewhat flattened costae with narrow interspaces, those on posterior area slightly weaker than on flanks. Commarginal sculpture of numerous fine growth ridges discernible only on early part of well preserved shells, and somewhat stronger ridges at later stages of growth. Cardinal area highly variable in size, ligamental chevrons fine and rather closely spaced; hinge teeth strongly inclined. Inner margin strongly crenulate.
Comparison: Tucetona lornensis is distinguished from younger species of Tucetona by its considerably smaller size and its relatively narrow intercostal spaces. Tucetona occurs widely in the Indo-West Pacific region and is represented in the modern New Zealand fauna by T. laticostata (Tongaporutuan ? Recent), which lives in coarse sand and gravel down to 75 m (Powell 1979, p. 365). Fossil occurrences indicate that this preference for a firm or hard substrate is characteristic of the genus. New Zealand species have usually been referred to Grandaxinea Iredale, 1931, but this is now regarded as a synonym of Tucetona Iredale, 1931 (Matsukuma 1980; 1986, p. 81); Tucetona is treated by Matsukuma as a full genus in Subfamily Melaxinaeinae.
Distribution: Kaiatan-Whaingaroan; Kaiatan, Waiareka Volcanic Formation, Lorne (type); Trig M, Totara; Deborah Volcanic Formation, Gee's Point, Kakanui; Cookson Volcanics, Lottery River, North 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)