GNS Science

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

New Zealand Cenozoic Mollusca

Semicassis pyrum (Lamarck, 1822)


(Pl. 48a): GS4068, R22/f6399, Kaimatira Pumice Sand, Kai-Iwi Beach, west of Castlecliff, Wanganui, Castlecliffian (GNS)

Beu & Maxwell (1990): Chapter 16; p. 353; pl. 48 a.

Synonymy: Cassis pyrum Lamark 1822, p. 226; Cassis nivea Brazier 1872, p. 616; Cassis striatus Hutton 1873b, p. 8 (not of J. Sowerby, 1812); Cassis tumida Petterd 1886, p. 321; Cassidea turgida "Reeve" of Hedley 1903, p. 340; Cassidea stadialis Hedley 1914, p. 72; Cassidea multisecta Finlay 1924a, p. 101 (new name for C. striatus Hutton, preoccupied); Xenogalea finlayi Iredale 1927, p. 342; Xenogalea powelli Finlay 1928b, p. 247; Xenophalium wanganuiense Powell 1928b, p. 637; Xenophalium hamiltoni Powell 1928b, p. 639; Xenophalium ericanum Powell 1928b, p. 639; Xenophalium harrisonae Powell 1928b, p. 640; Xenogalea denda Cotton 1945, p. 168; Xenophalium (Xenogalea) matai Powell 1952, p. 178; Xenogalea halli Cotton 1954, p. 2; Xenophalium (Xenogalea) abernethyi Dell 1956c, p. 87; Xenogalea pyrum; Xenophalium pyrum; Phalium pyrum

Type species of Xenogalea Iredale, 1927 (= Semicassis Morch, 1852)

Classification: Cassidae: Phaliinae

Description: Moderately large for subfamily (60-100 mm high), evenly oval and inflated, superficially almost smooth, with low spire and short, very strongly twisted anterior canal separated from previous whorl by deep, wide, concave groove, forming a prominent, ridge-margined fasciole. Sculpture of a few shallow grooves on spire in a narrow subsutural zone, and on base; many specimens have nodules around the shoulder angle, and a lower row of nodules is present on a few specimens. Aperture large, oval. Outer lip strongly curved, thick, reflected, with or without low nodules on inner edge; inner lip thick, raised over neck into thick, smooth, free-standing collar; with or without wrinkles and low transverse ridges on lower columellar area. Protoconch moderately large, conical, of 2.5 smooth, inflated whorls.

Comparison: Semicassis pyrum is common around New Zealand today, from shallow water off oceanic sand beach and in large bays, to the outer shelf on soft substrates, and from rises and banks near the Three Kings Islands to the Snares in the south. It also occurs commonly in southeastern Australia. The shell varies markedly in size, thickness, colour pattern, spire height, the presence or absence of ridges inside the outer lip, and the presence or absence of one or two rows of nodules around the shoulder, and the many subtly different, intergrading ecological forms have received many "species" names, but are of no biological significance. The Castlecliffian fossil multisecta form was based on immature specimens with a strongly dentate outer lip and relatively prominent spiral grooves over the entire last whorl, but these are identical to characters of immature Recent specimens.

Beu (1976c) showed that some specimens of the Stewart Island cool-water, thick-shelled harrisonae form of S. pyrum have intricately wrinkled inner lips as in typical Semicassis species. S. pyrum arrived abruptly in New Zealand during early Nukumaruan (latest Pliocene) time from the northern hemisphere, probably from a stock related to the European fossil S. laevigata (de Serres), and "Xenophalium" species are simply weakly sculptured species of Semicassis. In our opinion Semicassis is a genus distinct from Phalium, as it lacks the multiple varices (in all but a few unusual individuals) and complex sculpture, in most species axial or coarsely cancellate, of Phalium.

The closely similar species Semicassis labiata labiata (Te Piki bed, Cape Runaway, Haweran, oxygen isotope stage 7; and living in the northeastern North Island and in southeastern Australia; with weakly differentiated geographical subspecies in South America and South Africa) is smaller, taller and narrower, and more weakly sculptured than S. pyrum, with a much narrower groove between the canal and the last whorl, and the inner lip is plastered smoothly to the shell rather than raised into a free shelf or collar as in S. pyrum.

Distribution: Nukumaruan-Recent; Recent, Australia (types of Cassis pyrum, C. nivea, C. tumida, Cassidea stadialis, Xenogalea denda, Xenogalea halli); Recent, New Zealand (types of Xenogalea finlayi, X. powelli, Xenophalium harrisonae, X. hamiltoni, X. ericanum, X. matai, X. abernethyi); "Wanganui (U); Shakespeare Cliff; Puku-tapu(?)" (Hutton 1873b, p. 8), i.e., upper beds at Castlecliff, Wanganui, and Shakespeare Cliff (in Wanganui city), Castlecliffian (type of Cassis striatus, not of J. Sowerby, = Cassidea multisecta). The "Puku-tapu" locality apparently refers to Puketapu, central Hawke's Bay (Petane Group, late Nukumaruan), but we do not know of a specimen that Hutton's record was based on. "Wanganui (Upper Pliocene), Castlecliff", i.e., Castlecliff, Wanganui (unspecified horizon), Castlecliffian (type of Xenophalium wanganuiense). Rare in Nukumaruan rocks of Hawke's Bay and South Wairarapa, moderately common in Castlecliffian rocks at Wanganui and the Haweran Te Piki member, near East Cape.

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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