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. 7q): GS9508, J40/f8803, McCulloch's Bridge, Kaiatan (GNS) |
 (Pl. 7r): GS9508, J40/f8803, McCulloch's Bridge, Kaiatan (GNS) |
Beu & Maxwell (1990): Chapter 8; p. 127; pl. 7 q, r.
Synonymy: Architectonica ngaparaensis Suter 1917, p. 14
Classification: Architectonicidae
Description: Size moderate for family (diameter 8-12.5 mm), lenticular, spire very depressed but not flat. Protoconch heterostrophic, initial whorl immersed. Teleoconch of about 4 whorls that are flat or gently convex dorsally; last whorl sharply keeled, base moderately convex, with a wide, perspective umbilicus. Spiral sculpture consisting primarily of a narrow, finely beaded cord immediately above suture, becoming peripheral keel on last whorl, where it is joined by a narrow, smooth or feebly gemmulate cord a short distance below. A row of small gemmules, without a connecting thread on most specimens, below suture on some shells. Remainder of shell with weak or subobsolete threads. Axial sculpture, apart from gemmules margining suture, of growth lines which weakly gemmulate dorsal spiral threads on some shells. Umbilical border strongly crenulated by 24-30 axial folds. Umbilicus with a crenulated cord within in most specimens, ending somewhat above middle of inner lip, but cord absent from a few specimens. Aperture subquadrate.
Comparison: Wangaloa plana (Wangaloan, Wangaloa and Boulder Hill), the type species of the genus, has a less acute periphery and has much coarser sculpture (of short ridges rather than gemmules) margining the lower suture. Both species are readily distinguished from other New Zealand architectonicids by the relatively weakly developed spiral sculpture and by the very depressed spire. The genus Wangaloa has not been considered in Bieler's revisions of Architectonicidae. Maxwell's (1992, p. 170) treatment does not make it clear how Wangaloa differs from other similar, low-spired, weakly sculptured genera, but he compared it with the type species of Patulaxis Dall, 1892 (P. scrobiculata (Conrad, 1833), Middle Eocene, Alabama) and noted that Bieler (1985, p. 244) considered Patulaxis to be a synonym of Climacopoma Fischer, 1885.
Distribution: Kaiatan; "concretions with fossils overlying coal beds, Ngapara" (type — almost certainly from the Waihao Greensand, McCulloch's Bridge where it is not uncommon (see Maxwell 1966, p. 451; Maxwell 1992, p. 170); Kapua Tuff, Waihao River.
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)