Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 29h): paratype, GS2830, N33/f9106, Gower River, North Canterbury, Tongaporutuan (TM3775, GNS)
Beu & Maxwell (1990): Chapter 13; p. 262; pl. 29 h.
Synonymy: Zeacolpus (Zeacolpus) taranakiensis Marwick 1965, p. 48
Description: Moderately large for genus (25-65 mm high), tall and slender, with almost straight sides but outline weakly notched at deeply indented sutures; sculpture of very even, uniform, narrow spiral cords; most specimens are short lengths of shell only. Sutural ramp narrow, sloping very steeply, succeeded by wide, flat or gently concave mid- whorl area, occupying central 0.7 of whorl; another angulation near base formed by primary cord C, then contracting sharply to suture. Primary cords A, B and C are not distinguishable from evenly sculptured background in adults. Outer lip with wide, fairly shallow, V-shaped sinus, with rounded apex; base flat. Protoconch paucispiral, of 1 bulbous whorl, with a small initiation.
Comparison: Most specimens of Zeacolpus taranakiensis have less numerous and less regular, more widely spaced spiral cords than Z. pukeuriensis (Pl. 20a) and Z. fyfei (Lillburnian-Waiauan, Gisborne district) and lack the medially smooth zone of most Z. fyfei. Z. taranakiensis seems to have descended from Z. nisseni (Waiauan, Clifden, and Paparoa Rapids, Wanganui River), which differs in having two well differentiated, prominent cords around the basal angle, and finer spiral cords above. Z. taranakiensis is possibly on a line leading to Z. kanieriensis (Pl. 36n) and Z. vittatus (Pl. 47f). A few specimens have been collected in which the last whorl contains many juvenile shells, consisting of the one-whorl protoconch plus the first teleoconch whorl, indicating that the species was ovoviviparous (Marwick 1971b).
Distribution: Waiauan?; Tongaporutuan; coast at Omahu Trig., Mimi, North Taranaki (type), and abundant at most shallow-water Tongaporutuan localities in New Zealand, in Taranaki, Gisborne district, southern Hawke's Bay, Wairarapa, Marlborough, North Canterbury, and Westland. Potentially a very useful biostratigraphic index of Tongaporutuan age, but difficult to use in practice.
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)