Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 34i, j): GS4252, Q22/f7545, Middle Waipipi Shellbed, Waverley Beach, Wanganui, Waipipian (GNS)
Beu & Maxwell (1990): Chapter 14; p. 284; pl. 34 i, j.
Synonymy: Cardium spatiosum Hutton 1873b, p. 23
Type species of Maoricardium Marwick, 1944
Classification: Cardiidae: Cardiinae
Description: Extremely large for family (135-155 mm long), highly inflated, exceedingly thick and massive (shell of some specimens more than 17 mm thick near anterior ventral margin), relatively short, trigonally elongate at posterior ventral corner. Umbones strongly prosogyrous. Sculpture of 40 very prominent radial costae, anterior 10 low and rounded, increasing progressively in height to high, median ones of square section, posterior 6 lower and more closely spaced than others (defined largely by their rows of tubercles); all bear large, elongate to cup-shaped (ventrally convex) periostracal tubercles (only flat scars of former tubercles remain over most of disc, except around anterior, posterior and ventral margins, on large specimens). Inner ventral margin coarsely and deeply crenulate. Hinge wide and thick, with a high, massive, square-ended nymph plate in both valves, and 2 large, conical cardinal teeth and a median socket in each valve; left valve with 1 very large, conical anterior lateral tooth, only a weak socket above it, and a very small, flange-like posterior lateral tooth; right valve with moderately large anterior lateral tooth and a very small posterior lateral tooth. Adductor scars large, subcircular; pallial line without sinus.
Comparison: Maoricardium spatiosum is easily recognised by its enormous size, its very thick shell, its great inflation, and its sculpture of prominent radial costae. Specimens from high in the sequence at Clifden, Southland are intermediate between Maoricardium spatiosum and M. gudexi, being smaller and having lower, wider radial costae than typical Pliocene shells (Cucullaea Point shellbed and Lill Sand, Lillburnian; Nissen Shellbeds, Waiauan). M. gudexi is recorded from Altonian rocks in Canterbury, and was presumably the ancestor of M. spatiosum. M. spatiosum is also similar in most characters to the living East African Maoricardium pseudolima (Lamarck), which differs only in its more quadrate, more nearly symmetrical shape. The extinction of M. spatiosum and of Polinices waipipiensis is important for recognising the end of Mangapanian time in shallow facies.
Distribution: Lillburnian-Waiauan ?; Tongaporutuan-Mangapanian. "Waitotara", west of Wanganui, probably from Wilkies Shellbed at Wilkies Bluff, mouth of Waitotara River, Mangapanian, type (Boreham 1965, p. 58, pl. 16, fig. 1, 3; lectotype illustrated). Abundant in the Middle and Upper Waipipi Shellbeds at Waverley Beach, west of Wanganui (Waipipian), and common in many other Pliocene shellbeds near Wanganui, such as the Mangapani Shell Conglomerate and Wilkies Shellbed (both Mangapanian); widespread but uncommon in shallow, soft-bottom facies of Opoitian to Mangapanian age at Kaawa Creek and Otahuhu well near Auckland, and in Wanganui, Hawke's Bay, and North Canterbury. A few specimens are known from rocks as old as Kapitean (Mangatuna quarry, inland from Tolaga Bay) and Tongaporutuan (Tokomaru Bay; Hurupi Stream, Palliser Bay).
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)