Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 14m): GS7166, I40/H551, Brother's Stream, Hakataramea Valley, Waitakian (GNS)
(Pl. 14n): GS7166, I40/H551, Brother's Stream, Hakataramea Valley, Waitakian (GNS)
Beu & Maxwell (1990): Chapter 10; p. 156; pl. 14 m, n.
Synonymy: Onustus prognatus Finlay 1926b, p. 228
Description: Moderately to very large for family (diameter 80-140 mm or more, including attached objects), trochiform, spire low, almost straight-sided; edge of upper surface projecting as ridge (or rim) around edge of flat or slightly concave base; no umbilicus. Sculpture on upper surface of rather indistinct, low, narrow, wavy collabral ridges and spiral cords; on base, of low, collabral ridges and very weak spiral threads. Attached objects consisting of large pebbles, concave-side-up bivalves (up to 50 mm wide) and much rarer gastropods, cemented into rim of each whorl, so forming part of upper surface of succeeding whorl. Aperture very low and wide, subrectangular; lower lip deeply excavated.
Comparison: Topotypes of Xenophora prognata are among the largest known xenophorids ("carrier-shells"), commonly reaching 120 mm or more in diameter, but smaller specimens from other localities show no differences other than size. X. neozelanica (Opoitian-Recent) differs in its markedly taller spire and coarser basal sculpture. A quite distinct species is X. flemingi (Altonian-Clifdenian and possibly Lillburnian, Clifden and North Taranaki), which has flat sides, weak sculpture and very small attached objects. X. neozelanica occurs today on soft substrates on the shelf, in depths of about 10-150 m, and X. prognata seems to have lived in similar shallow facies. X. flemingi occurs in deeper-water siltstone, and at Clifden it occurs in different beds from X. prognata.
Distribution: Runangan-Lillburnian; "Wharekuri Greensands", Duntroonian (type probably from Waitaki River, opposite Wharekuri), and from numerous localities throughout New Zealand (Beu 1977b).
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)