GNS Science

Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)

New Zealand Cenozoic Mollusca

Cosmasyrinx monilifera Marwick, 1931


(Pl. 27s): holotype, GS1293, Y17/f7472, Akiripuraho Stream, tributary of Waihora River, near Kanakanaia Road, 4 km northeast of Te Karaka, Gisborne, Altonian or Clifdenian (TM 6801, GNS)

Beu & Maxwell (1990): Chapter 12; p. 250; pl. 27 s.

Synonymy: Cosmasyrinx monilifera Marwick 1931, p. 138

Type species of Cosmasyrinx Marwick, 1931

Classification: Turridae: Cochlespirinae?

Description: Small for family (12-15 mm high), with moderately tall, weakly stepped spire, long straight unnotched anterior canal, wide almost smooth sutural ramp, and wide, moderately deep posterior sinus occupying sutural ramp, with its rounded apex near centre of ramp. Sculpture dominated by row of small nodules around prominent peripheral band of three closely spaced spiral cords, by 2 or 3 prominent smooth cords lower on last whorl, and by low, almost smooth subsutural cord; neck and canal bearing a further 14 low spiral threads. Protoconch dome-shaped, of 2 apparently smooth whorls with large, bulbous apex.

Comparison: Cosmasyrinx monilifera is illustrated as an example of a widespread genus of Miocene bathyal faunas in Gisborne district, Wairarapa and Westland. "Cosmasyrinx" semilirata (Duntroonian, coast near Orepuki, Southland) has a raphitomine protoconch (with characteristic decussate (diagonally reticulate) sculpture) and was placed by Beu & Maxwell (1990) in Cryptodaphne; all remaining species of Cosmasyrinx are Miocene. Several lots of Cosmasyrinx collected in the Gisborne district in recent years show that there are probably several unnamed species, and shells reach 20-25 mm in height. Unnamed, relatively narrow species from the Stillwater Mudstone (Clifdenian-Waiauan) in Westland resemble Gemmula species, but differ in their low, dome-shaped (rather than narrowly conical) protoconch, and in the anal sinus occupying the sutural ramp, not the peripheral keel (suggesting a possible relationship with Cochlespira rather than Gemmula). Typical Gisborne species of Cosmasyrinx differ further from Gemmula in their wide, almost smooth subsutural ramp. C. ardua is narrower than C. monilifera, with a more steeply sloping sutural ramp; C. latior has a strongly beaded subsutural cord; C. tereumera has larger peripheral nodules and more numerous spiral cords on the base than on C. monilifera; and C. marwicki (Tongaporutuan, southern Wairarapa) is similar to but more finely sculptured than C. tereumera.

Distribution: Altonian-Clifdenian; Akiripuraho Stream, Waihora River, Gisborne district, Altonian or Clifdenian (type); rare in bathyal siltstone of the Gisborne district.

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
ISBN 978-0-478-19705-1
ISSN 1177-2441
(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)


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