Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 30h): GS1037, S28/f6446, Whatarangi Cliffs, east of Putangirua Stream, eastern Palliser Bay, southern Wairarapa, early Tongaporutuan (GNS) (a young specimen with a relatively weakly developed shoulder roll).
Beu & Maxwell (1990): Chapter 13; p. 267; pl. 30 h.
Synonymy: Cominella hendersoni Marwick 1926c, p. 322
Description: Small for genus (28 to 35 mm high), short and wide, with moderately to very short spire (little elevated above top of outer lip, to quarter height of aperture), almost vertical-sided last whorl, a greatly thickened parietal callus at top of aperture, swelling in mature specimens to massive, roll-like collar around top of last whorl to form rounded shoulder that protrudes strongly above suture and, in older adults, above most of spire. Fasciole very wide, convex, with coarsely lamellose sculpture, reflecting very deep siphonal notch. Spire moderately tall in young shells, but becoming progressively reduced in older ones as shoulder becomes more elevated. Sculpture of many low, wide, weakly convex spiral cords, with moderately wide interspaces (each about equal to width of 1 cord) crossed by fine growth lamellae; the only other axial sculpture is low costae on very early spire whorls in most specimens, although C. crassinodosa (Marwick, 1931) is possibly a form of C. hendersoni retaining nodules onto last whorl. Protoconch not preserved on available material; presumably as in C. adspersa, of 2 smooth, strongly inflated whorls, with a blunt apex.
Comparison: The taxonomy of the Miocene short, square-sided, roll-shouldered fossils apparently ancestral to the living Cominella adspersa is poorly understood; the great variation of C. adspersa suggests there are fewer true fossil taxa than nominal species. It seems likely that the small forms, developing a shoulder roll by about 26-28 mm high, are one species (C. hendersoni; ? = C. crassinodosa; ? = C. ridicula; Altonian- Tongaporutuan). The Altonian C. errata (= Buccinum carinatum Hutton, 1873, not of Turton, 1819) is distinct; typical specimens (basal shellbed of Enys Formation, junction of Porter and Thomas Rivers, Castle Hill Basin, Canterbury) reach a much larger size (height 50 mm) and are still more square-sided and roll-shouldered than C. hendersoni. C. scirrifer (Altonian, Sutherlands, Tengawai River, Canterbury) belongs in a different group with a taller, conic spire, large shoulder nodules, and only a weakly developed shoulder roll, although specimens similar to C. errata occur with it at Sutherlands. Pliocene species (C. facinerosa, Opoitian, Kaawa Creek, southwest Auckland; C. dingleyi, Waipipian, Otahuhu Brewery well, Auckland) appear to belong in a lineage that increased progressively in size, culminating in the "giant" species C. kereruensis (Mangapanian-Nukumaruan, Wanganui and Hawke's Bay), which is larger (75-80 mm high) and has stronger spiral cords than the Castlecliffian to living species C. adspersa. A few specimens of C. adspersa reach 68-70 mm high, but most specimens over 45-50 mm high are starting to develop a shoulder roll, although it is always less prominent in this species than in the Miocene fossils.
Distribution: (Altonian?, Clifdenian?) Lillburnian-Tongaporutuan; Tirangi Stream, North Taranaki, Tongaporutuan (type of Cominella hendersoni); "band 6c" (Slip Point Siltstone?), Clifden, Southland, Clifdenian ? (type of Acominia ridicula ); "Tutamoe conglomerate", Pangopango Stream, inland from Tolaga Bay, Gisborne district, Lillburnian (type of Cominella crassinodosa); uncommon in the Southland Series, in the more shallow-water facies at Clifden, Southland, and in the Gisborne district; and abundant in near-shore, soft-bottom facies of Tongaporutuan age in Wairarapa (notably at Palliser Bay, but also further north), North Taranaki, and in the Gisborne district. Some specimens from Palliser Bay show the remnants of a speckled colour pattern preserved as brick-wall-like markings on the spiral cords.
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)