Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 28a): an unlocalised, complete specimen, from collection of H. Evans (probably from North Taranaki Tongaporutuan; GNS)
Beu & Maxwell (1990): Chapter 13; p. 254; pl. 28 a.
Synonymy: Nucula otamaringaensis Marwick 1926c, p. 327; "Ennucula" otamaringaensis, Beu & Maxwell 1990, p. 254, pl. 28a.
Classification: Nuculidae: Nuculominae
Description: Very large for family (23-31 mm long), thick but nacreous and fragile, highly inflated, oval; umbones strongly incurved and directed backward (opisthogyrous), situated at posterior quarter of length. Antero-dorsal margin strongly convex, with well defined, large lunule bounded by shallow, wide groove that forms shallow depression in valve margin; postero- dorsal margin excavated below umbones, then weakly convex above narrowly rounded posterior end. External sculpture of many fine radial threads crossing many slightly more prominent commarginal ridges. Valve margins smooth; hinge not seen (all specimens articulated).
Comparison: The very large size, the smooth margin, and the unique combination of fine radial and commarginal sculpture of almost equal prominence show that "Leionucula" otamaringaensis belongs in an unnamed genus of Nuculidae Nuculominae, and effectively distinguish it from all other New Zealand nuculids. Other, probably unnamed species of the group occur in Runangan to Otaian rocks.
Although Maxwell (1988b, 1992) and Beu & Maxwell (1990) cautiously retained Ennucula Iredale, 1931 for the widespread genus of large nuculids with a smooth internal margin (subfamily Nuculominae), resembling "Ennucula" otamaringensis but lacking radial sculpture, several other recent authors have accepted that Leionucula Quenstedt, 1930 is an earlier name for this genus, including Spencer et al. (2009). We now adopt Leionucula here.
Distribution: Tongaporutuan-Opoitian; coast near mouth of Waiau Stream, North Taranaki, Tongaporutuan (type); widespread in bathyal siltstone facies in Taranaki, Gisborne district, Wairoa district, southern Wairarapa, North Canterbury, and Westland.
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)