Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
| | Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990) |
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  (Pl. 40a): lectotype, Nukumaru Beach, Wanganui, Nukumaruan (TM4736, GNS) |
 (Pl. 40e): lectotype, Nukumaru Beach, Wanganui, Nukumaruan (TM4736, GNS) |
Beu & Maxwell (1990): Chapter 15; p. 313; pl. 40 a,e.
Synonymy: Amphidesma (Taria) crassiformis Marshall and Murdoch 1920, p. 136
Classification: Mesodesmatidae
Description: Large for genus (80 mm long), exceedingly thick and solid, with long, rounded anterior end but very short, squarely truncated posterior end. Anterodorsal, ventral, and posterior margins all lightly curved, meeting at almost right angles at umbo and postero-ventral corner. Prominent, weakly bi-angled ridge extending from umbo to postero-ventral corner; exterior otherwise sculptured only with weak growth ridges. Hinge exceedingly thick and deep (much the thickest of any mesodesmatid we are aware of), with long, narrow, deep, vertical, parallel-sided resilifer below umbo, thin anterior cardinal lamella above top of resilifer in each valve (other cardinal teeth broken off all specimens seen), and in right valve 2 exceedingly massive anterior and 2 similar posterior lateral teeth, each pair margining an exceedingly wide, deep socket for equally massive lateral teeth of left valve. Adductor scars almost equal, deeply impressed. Pallial line only weakly sinuous, except for small, shallow, almost square sinus in front of posterior adductor scar.
Comparison: Paphies crassiformis is an extremely unusual species, easily recognised by its thick shell and massive hinge; it is known only from near-estuarine muddy facies, so may have inhabited an unusual environment that was rarely preserved.
Distribution: Nukumaruan; "blue clays", Nukumaru Beach, Wanganui (type), almost certainly from the Tewkesbury Formation; rare at Nukumaru, uncommon at a few localities in the Rangitikei River section, and in Okauawa Stream, Kereru Road, inland central Hawke's 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
ISBN
978-0-478-19705-1
ISSN 1177-2441
(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)