GNS Science

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

New Zealand Cenozoic Mollusca

Gemmula peraspera Marwick, 1931


(Pl. 27m): holotype, GS1322, X17/f9474, small tributary of Totangi Stream 1.6 km north of major bend in Totangi Road, Ngatapa, northwest of Gisborne, Tongaporutuan (TM 6797, GNS)

Beu & Maxwell (1990): Chapter 12; p. 249; pl. 27 m.

Synonymy: Gemmula peraspera Marwick 1931, p. 133; ? = Gemmula orba Marwick 1931, p. 133

Classification: Turridae: Turrinae

Description: Moderate-sized for genus (27-33 mm high), tall and narrow, with narrow spire 0.5-0.6 total height; whorls prominently keeled at about mid-height on spire, forming narrow, strongly concave sutural ramp. Sculpture of peripheral row of small nodules, quite sharply pointed on most specimens, 16-20 per whorl; nodules are formed at apex of anal sinus, where growth lines curve sharply forward after their backward inclination over sutural ramp; spiral sculpture of 2 or, in most specimens, 3 prominent, widely spaced cords on base, narrow, weakly gemmate subsutural cord, 3 to 5 low threads on sutural ramp, 3 narrow threads over peripheral nodules, and about 20 low, closely spaced cords on anterior canal. Anterior canal long and narrow, deflected weakly to left, but incomplete on all known specimens. Protoconch presumably as in other Gemmula species, narrowly conical, of 5 or 6 whorls, smooth near apex but with regular axial costae lower down.

Comparison: Marwick (1931, p. 133) named both Gemmula peraspera and G. orba from GS1322, Totangi Stream, Ngatapa, Gisborne, and other specimens resembling the holotype of G. orba have not been collected subsequently. Comparison of the holotypes showed few differences other than the lower spire and more prominent subsutural cord of G. orba , and it seems likely that the holotype of G. orba is a broken, low-spired specimen of the species also named G. peraspera. Fleming (1966b, p. 114, caption to Bathyarca crenulifera) noted that although matrix supposedly from GS1322 contained Lillburnian foraminifera, the nearby GS1332 is Tongaporutuan, the faunas of GS1322 and GS1332 are almost identical, and it seems likely that GS1322 is really Tongaporutuan. The subsequent collection of G. peraspera from rocks of Tongaporutuan to Opoitian (not Middle Miocene) age helps to confirm Fleming's conclusion.

Gemmula peraspera is a member of a group of small to moderate-sized, tall-spired, finely sculptured Gemmula species that is common in New Zealand Neogene rocks. The most closely similar species are G. kaiparaensis, with two cords around the peripheral keel, and the smaller, narrower, very finely sculptured G. clifdenensis (Pl. 26g), with two or three relatively prominent cords around the peripheral keel.

Distribution: Tongaporutuan-Opoitian; Totangi Stream, Ngatapa, Gisborne district, Tongaporutuan (type); widespread in bathyal siltstone in Gisborne district, Wairoa district, and southern Wairarapa. Curiously, although it is common at most southern Wairarapa Tongaporutuan localities, specimens have not been collected at Bell's Creek, Mangaopari Stream, the locality with the most diverse faunule (Beu 1970c, p. 232).

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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