Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 19d, e): GS9700, J38/f9681, Sutherlands, Tengawai River, Altonian (GNS)
Beu & Maxwell (1990): Chapter 11; p. 186; pl. 19 d,e.
Synonymy: Cardium (Trachycardium) cantuariense Laws 1933, p. 317; Hedecardium cantuariense
Type species of Titanocardium Maxwell, 1978
Classification: Cardiidae: Protocardiinae
Description: Very large for family (length 75-105 mm), rather thin-shelled, highly inflated; posterior area well defined. Posterior end truncate, with a distinct siphonal gape. Lunule well defined. Anterior and median regions with radial sculpture of about 45 low, rounded or flat-topped costae, those near middle of shell with a shallow longitudinal groove distally, interspaces considerably wider anteriorly than in middle of shell. Posterior area with about 15 costae with narrow interspaces, more subdued than those on rest of shell, and becoming obsolete near posterodorsal margin. Commarginal sculpture of weak growth lines. Hinge similar to that of Hedecardium waitakiense (Pl.13d,e).
Comparison: Hedecardium cantuariense is not particularly common at any locality, but is conspicuous because of its large size. H. (Titanocardium) greyi (Otaian, Auckland) grows to a larger size than H. cantuariense (length up to 120 mm), has more widely spaced costae (particularly in the middle of the shell) and has a much narrower siphonal gape. H. (Titanocardium) marwicki (Lillburnian-Waiauan or Tongaporutuan, Clifden and Wairarapa) is more similar to H. cantuariense than is H. greyi, but differs in having a broader lunule and in having the radial costae in the middle of the shell triangular in section and lacking a longitudinal groove. The subgenus Titanocardium differs from Hedecardium (sensu stricto) in its much larger size and, more significantly, in having a distinct posterior gape.
Distribution: Altonian; Southburn Sand, Sutherlands, Tengawai River (type); White Rock River; Ardgowan Shellbed, Oamaru.
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)