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. 22r): GS9500, J41/f8028, excavation for Oamaru Borough Council septic tank, South Oamaru, Altonian (GNS) |
Beu & Maxwell (1990): Chapter 11; p. 212; pl. 22 r.
Synonymy: Leucosyrinx alta transenna Suter 1917, p. 44; Phenatoma (Cryptomella) transenna; Tomopleura (Tomopleura) transenna, Beu & Maxwell 1990, p. 212, pl. 22r.
Type species of Cryptomella Finlay, 1924, synonymised with Tomopleura Casey, 1904 by Powell (1942, p. 110)
Classification: Conidae: "Clathurellinae" clade 14 (Puillandre et al. 2008; although it is doubtful whether New Zealand fossil species belong in the same clade as tropical Indo-Pacific species)
Description: Small for subfamily (height 8-11 mm), narrowly biconic, spire pagodiform, 0.6 total height. Protoconch narrowly conical, of 4.5 whorls, a weak subangulation appearing at about a quarter whorl height on 3rd whorl, gradually becoming more marked, last whorl with well developed keel somewhat below middle, and weak opisthocyrt costellae on ramp on last quarter-whorl. Teleoconch of 5-6 whorls, sharply keeled at about 0.4 whorl height on spire, sutural ramp broad, steep, slightly concave, whorl sides sloping inwards. Last whorl with peribasal angulation or subangulation, strongly excavated below, neck short. Spiral sculpture commencing as a prominent, rounded, smooth cord on periphery, accompanied by a much weaker one margining lower suture and another just below upper suture on most specimens. Additional spirals appearing during growth, penultimate whorl with 3-5 narrow cords or threads on ramp, 1 or 2 near upper edge stronger than others on many specimens, and a cord or thread between periphery and lower suture. Last whorl with supramargining cord emerging on peribasal angulation, and 12-15 cords, some with interstitial threads, on base and neck. Axial sculpture of relatively prominent and numerous growth lines. Aperture small, pyriform; columella strongly twisted near middle, almost straight above, concave below; siphonal canal short, shallowly notched. Inner lip smooth, strongly impressed; outer lip thin, with a moderately deep, strongly assymetric anal sinus, its apex low down on ramp.
Comparison: Tomopleura finlayi (Altonian, Ardgowan Shellbed) is similar to T. transenna in sculptural plan, but the spiral sculpture — particularly the peripheral cord — is considerably stronger in T. finlayi. T. excavata (Altonian, White Rock River, Sutherlands, Target Gully and Ardgowan Shellbeds) is much more distinct, having a much broader shell than T. transenna, a less prominent peripheral keel (scarcely stronger than the basal cords) and more numerous and more closely spaced cords on the base and neck.
Tomopleura has a range of Wangaloan to Recent in New Zealand, and is supposedly congeneric with tropical Indo-Pacific species, although it seems unlikely that the small New Zealand species belong in the same clade as the much larger tropical Recent species. The genus Cryptomella probably deserves to be resurrected for New Zealand species. A subgenus Tomopleura (sensu stricto) (Wangaloan to Waiauan) traditionally has been segregated from a subgenus T. (Maoritomella), which differs only in having a paucispiral rather than a conical protoconch, but this is a classic case of several species losing planktotrophy independently, and acquiring paucispiral protoconchs as a result. There is no doubt that T. (Maoritomella) is of no phylogenetic significance.
Distribution: Otaian-Altonian; Mount Harris Formation, Awamoa, Oamaru, Altonian (type); Pukeuri; excavation for Oamaru Borough Council septic tank, South Oamaru; Oneroa, Waiheke Island; Pakaurangi Point.
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)