Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 20e): GS5591, J38/f9498, Sutherlands, Tengawai River, Canterbury, Altonian (GNS; specimen figured by Marwick 1971a, pl. 8, fig. 11)
Beu & Maxwell (1990): Chapter 11; p. 188; pl. 20 e.
Synonymy: Turritella (Haustator) concava Hutton 1877b, p. 597 (not of Say, 1826, etc.); T. (Colpospira) concava; T. (Zaria) abscisa Suter 1917, p. 8; T. albolapis Finlay 1924a, p. 101 (new name for T. concava Hutton, preoccupied); Zeacolpus albolapis; Tropicolpus albolapis; Zeacolpus abscisus
Type species (as T. albolapis) of Tropicolpus Marwick, 1931
Description: Large to very large for family (height 70-150 mm), robust. Protoconch mamillate, of 2.5 smooth whorls. Teleoconch of about 20 whorls, earliest whorls biangulate, quickly becoming strongly keeled below middle, keel soon becoming obsolete; subadult whorls concave, adult whorls subquadrate, telescoped, swollen adapically, gently concave below. B and C commencing at beginning of teleoconch, subequal at first, but C surpassing B on about 3rd whorl, B fading into background by about 6th, C by about 12th whorl. Cord A remaining insignificant throughout growth. Subadult and adult whorls with a broad, low cingulum at about 0.67 whorl height, and numerous fine, subuniform spirals below. Outer lip sinus moderately deep, assymetrical, apex at or somewhat above middle, abapical limb becoming progressively more strongly convex during growth.
Comparison: Tropicolpus abscisus is differentiated from other "giant" mid-Cenozoic turritellids by the submedially keeled early teleoconch whorls, by the more or less telescoped later whorls and by the tendency for the abapical limb of the sinus in the outer lip to become strongly convex in the adult. T. milleri (Altonian?, Clifdenian to Tongaporutuan, East Coast, North Island) is possibly conspecific, although it includes individuals with a very heavy adapical cingulum and strongly concave adult whorls, reaching a particularly large size.
Distribution: Altonian; "Oamaru" (type locality of T. abscisa probably Mount Harris Formation, Old Rifle Butts, Cape Wanbrow); Southburn Sand, White Rock River (type locality of T. concava) and other localities in North Otago, Canterbury and southern Marlborough. Most common in shallow-water sandstone and shellbeds.
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)