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. 22m): GS5177, J38/f9526, Tengawai River near Sutherlands, South Canterbury, Altonian (GNS) |
Beu & Maxwell (1990): Chapter 11; p. 211; pl. 22 m.
Synonymy: Clavatula haasti Hutton 1877b, p. 595; Bathytoma (Bathytoma) haasti, Beu & Maxwell 1990, p. 211, pl. 22m.
Classification: Conidae: "Clathurellinae" clade 20 (Puillandre et al. 2008)
Description: Size moderate for genus (height 30-55 mm), biconic, spire 0.45- 0.5 total height. Protoconch conical, of 3.5 convex whorls, last 0.8 whorl with opisthocyrt costellae, remainder smooth. Teleoconch of 7-8 whorls, prominently shouldered at, or more typically below, middle on spire; sutural ramp concave with slight subsutural swelling, whorl sides sloping sharply inwards. Last whorl excavated, with short neck. Axial sculpture of numerous, narrow, straight or slightly arcuate tubercles with considerably wider interspaces, on narrow peripheral band; some shells with more numerous, short, prosocline ridges on subsutural swelling as well; growth ridges numerous, moderately prominent. Penultimate whorl with about 30-50 peripheral tubercles. Spiral sculpture complex, penultimate whorl with 2 or 3 narrow, rounded cords on peripheral tubercles, and numerous finer cords and threads on ramp, 2 or 3 on subsutural swelling typically stronger than others. Base and upper part of neck with 10-15 narrow, well spaced cords, as strong as or stronger than peripheral cords, the uppermost exposed on penultimate whorl of some shells, with 1-3 threads between each pair. Lower part of neck with closely spaced, narrow cords. Most, if not all, spirals finely nodulose. Aperture elongate, columella weakly twisted near middle, some shells with a low fold on twist; siphonal canal short, shallowly notched. Outer lip thin, with broadly V-shaped anal sinus, its apex rounded, on peripheral band.
Comparison: Bathytoma haasti belongs to a different species group from B. bartrumi (Pl. 26j) and B. finlayi (Altonian-Lillburnian, Clifden), differing from them in having finer, more rounded peripheral tubercles, and finer, more numerous spiral cords. A closely related species from Waitakian siltstone (Mount Harris Formation) in the upper Tengawai River differs from typical B. haasti in having a more slender shell and considerably finer and more numerous spiral cords on the last whorl. It may be conspecific with the poorly known B. hokianga (Otaian, Hokianga Harbour area, Northland).
Bathytoma haasti is remarkably similar to the type species of Bathytoma, B. cataphracta (Brocchi, 1814) (Pliocene, Europe), differing mainly in rather minor sculptural characters and in having a less pronounced columellar fold. Traditionally a subgenus Bathytoma (Micantapex) has been recognised for species with a blunt, paucispiral protoconch, whereas Bathytoma (sensu stricto) was used for species with a conical protoconch of 3.5 or more whorls, but this purely developmental difference is no longer considered to separate clades, and species assigned to Micantapex clearly have evolved from species with a conical protoconch by loss of planktotrophy through Cenozoic time. The genus ranges from Waitakian (possibly Duntroonian) to Recent in New Zealand.
Bathytoma is most characteristic of moderately deep-water (outer shelf or upper bathyal) assemblages, but B. haasti is common in the shallow-water Southburn Sand at Sutherlands, and B. finlayi is not uncommon in shallow-water units at Clifden.
Distribution: Otaian-Altonian; Mount Harris Formation, Mt Harris, South Canterbury, Otaian or Altonian (type); Bluecliffs, Otaio River; foot of Mt Horrible, Pareora River; Southburn Sand, Sutherlands; Ardgowan Shellbed, Oamaru; Awamoa Creek; Otahu Formation, Clifden. Considerably more common at South Canterbury than at North Otago localities.
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)