Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 14f): GS11196, I40/fl63, top of section at head of Lake Waitaki, Waitaki Valley, Duntroonian or Waitakian (GNS)
Beu & Maxwell (1990): Chapter 10; p. 156; pl. 14 f.
Synonymy: Zeacolpus grindleyi Marwick 1971a, p. 32
Description: Small for family (height 12-16 mm), narrowly conical. Protoconch very difficult to distinguish from teleoconch, turbinate, apparently of slightly more than 1 convex whorl, apex moderately exsert. Teleoconch whorls about 9, the first few gently convex, later ones flat-sided except for a weakly projecting cord margining lower suture and emerging on last whorl as peripheral keel; base flat or slightly concave. Spiral sculpture very feeble, scarcely distinguishable on some shells, 1 thread somewhat more prominent than others on a few specimens. Outer lip sinus moderately deep, apex well above middle of whorl, basal growth lines shallowly concave towards aperture.
Comparison: Gazameda grindleyi is readily distinguished from all other New Zealand turritellids by its small size, its flat-sided adult whorls, its concave base and its very weak or obsolete sculpture. Although described as a species of Zeacolpus (sensu lato), it is much closer to some Australian species of Gazameda, particularly the Middle Miocene taxa G. victoriensis victoriensis (Cotton and Woods, 1935) and G. victoriensis manyung Garrard, 1972 (see Garrard 1972, pl. 28, fig. 16, 17) and is considered to be congeneric. G. grindleyi is the only New Zealand member of the genus we are aware of. The classification of Turritellidae is highly uncertain, and will only be resolved by molecular techniques, because of the large number of similar species over its Cretaceous-Recent time range and the few shell characters available for classification. It seems likely that both Zeacolpus and Gazameda (= Stiracolpus?) are derived from Haustator, but much research is required on this family.
Distribution: Duntroonian, Waitakian?; Wharekuri Greensand, Waitaki River, opposite Wharekuri (type); head of Lake Waitaki (not uncommon near top of section).
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)