Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
| | Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990) |
|
  (Pl. 42f): GS1098, V21/f8490, one of the specimens collected by Marwick and Uttley in 1924 from "a sandy pocket of the clays not far below the [Nukumaruan] limestone at Maraekakaho, Ngaruroro River", central Hawke's Bay, Nukumaruan (TM5766, GNS) |
Beu & Maxwell (1990): Chapter 15; p. 318; pl. 42 f.
Synonymy: Struthiolaria frazeri Hutton 1885b, p. 329
Classification: Struthiolariidae
Description: Large for genus (65-90 mm high), with very tall spire for family (slightly taller than aperture), strongly shouldered whorls, and a normal round Struthiolaria aperture with heavily thickened, strongly sinuous outer lip, heavily thickened and relatively wide inner lip with wide parietal callus, and shallow anterior notch. Sculpture of very prominent, wide spiral cords of almost square section, 3 closely spaced on sutural ramp, 1 particularly prominent (bifid and weakly nodulous on most specimens) around shoulder angle, 4 widely spaced on whorl sides, and a further 6 or 7 decreasing in prominence down base. Protoconch not seen, but presumably as in S. papulosa (Pl. 47r).
Comparison: Struthiolaria frazeri is similar to the Mangapanian-Recent species S. papulosa (Pl. 47r) but differs in its much taller spire, very much more prominent spiral sculpture, and more heavily thickened aperture. An apparently ancestral, smaller, rather more weakly sculptured form is abundant in Mangapanian sandstone between the Napier-Taupo road and Mohaka River, northern Hawke's Bay and in early Nukumaruan sandstone near Sherenden, central Hawke's Bay. Beu (2009) interpreted this earlier but intergrading form as indicting anagenetic evolution of the extreme, late Nukumaruan form of S. frazeri from a form nearer to S. papulosa. S. frazeri is an extremely distinctive index species of Mangapanian and Nukumaruan age.
Distribution: Mangapanian-Nukumaruan; Kikowhero Stream, Matapiro Station, north side of Ngaruroro River, Hawke's Bay, Nukumaruan (type); common at very many localities of shallow-water, sandy facies (usually found as concentrated monospecific lenses) throughout the Nukumaruan rocks of central Hawke's Bay, and particularly abundant in a shellbed (the lower of two Struthiolaria-dominated shellbeds; the upper contains only S. papulosa) cropping out widely in road cuts on Kereru Road and in Okauawa and Whanakino Streams, inland central Hawke's Bay. Extensive collecting by many people over more than 100 years has produced only one or two specimens from Wanganui basin; we are aware of none from localities further south than the Kereru district, Hawke's Bay (the record from North Canterbury (Marwick 1924b, p. 182) has never been confirmed). Uncommon in Mangapanian and early Nukumaruan sandstone at a few localities in northern Hawke's Bay.
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)