Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 31f): holotype (TM1411, GNS; anterior valve), Otahuhu Brewery well, Auckland, Waipipian
(Pl. 31i): paratype, Otahuhu Brewery well, Auckland, Waipipian (TM1412, GNS)
(Pl. 31j): paratype, Otahuhu Brewery well, Auckland, Waipipian (TM1413, GNS)
Beu & Maxwell (1990): Chapter 14; p. 274; pl. 31 f,i,j.
Synonymy: Acanthochiton flebilis Laws 1950, p. 28
Description: Shell small (each valve to 6.0 mm wide, 3.6 mm long), valves relatively short and wide; most characters as in Notoplax mariae (Pl. 44a, d, h). Anterior valve (holotype) semicircular, with five very weak radial angulations representing radial costae. Median valves with rather small sutural laminae, clearly triangular jugum bearing faint longitudinal grooves and ridges, no radial ridge between pleural and lateral areas, and very fine tegmental granules. Posterior valve very small, with mucro slightly nearer posterior than in A. zelandica, with fine tegmental granules, and with a prominent radial fold on each side.
Comparison: The longitudinally striate juga of valves 2-8, the wide tegmental area, and the relatively small posterior valve suggest that Acanthochitona flebilis is related to the rare modern species A. thileniusi Thiele, 1909 (known only from a few specimens collected living intertidally on hard substrates at Mount Maunganui, Tauranga). A. flebilis differs from A. thileniusi in having more triangular median valve tegmenta, less like the very wide ones of A. rubiginosa than are those of A. thileniusi, and in having a much narrower, more subcircular posterior valve; the posterior valve of A. thileniusi is very wide. A. flebilis was certainly correctly referred to Acanthochitona, and is strongly distinct from A. zelandica.
Distribution: Waipipian, Otahuhu Brewery well, Auckland (type), very common; not definitely known from any other locality. The richly diverse shellbed encountered in the Otahuhu well (Marwick 1948; Laws 1950) contains only shallow-water, near-shore taxa, including a number of estuarine and rocky-shore molluscs. Acanthochitona flebilis almost certainly lived attached to rocks.
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)