Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 22n): GS11154, J39/f26, foot of Mt Horrible, Pareora River, South Canterbury, Otaian (GNS)
Beu & Maxwell (1990): Chapter 11; p. 213; pl. 22 n.
Synonymy: Ptychatractus nodosoliratus Suter 1917, p. 25
Classification: Conidae: "Clathurellinae" clade 13 (Puillandre et al. 2008)
Description: Size moderate for subfamily (height 10-12 mm), narrowly fusiform, spire about half total height. Protoconch narrowly mamillate, of about 1.5 smooth whorls. Teleoconch of about 6 whorls, broadly angled near middle on spire, sutural ramp steep, almost flat; last whorl weakly excavated. Axial sculpture of narrow, rounded, orthocline or slightly opisthocline costae with broader interspaces, reaching from suture to suture on spire (though weaker on ramp than below), dying out on upper part of base on last whorl, in some shells becoming obsolete on last half whorl; 12-14 on penultimate whorl. Spiral sculpture highly variable, of low flat-topped cords with occasional interstitial threads and threadlets, typically less well developed on ramp than below, slightly thickened or nodular where they cross axial costae; 3-6 on penultimate whorl, 14-18 more on base and neck of last whorl. Aperture narrow, columella slightly convex with 2 low plaits posteriorly. Outer lip with a very weak concavity on ramp, lirate within.
Comparison: Vexithara vexilliformis (Altonian, Pukeuri road cutting, Oamaru) the type species of the genus is smaller and less slender than V. nodosolirata, and has less prominent spiral sculpture (almost obsolete on spire whorls on some shells). V. magna (Waitakian, Hakataramea Valley) is considerably larger than either V. nodosolirata or V. vexilliformis, and has four rather than two columellar plaits. Vexithara is very similar to Mitrolumna, differing mainly in having distinctly shouldered rather than convex whorls, and in having relatively strong axial sculpture. Therefore, it probably belongs in the same clade as Mitromorpha (clade 13, "Clathurellinae"; Puillandre et al. 2008, fig. 1) although the classification of Conoidea is in a state of flux at present.
Distribution: Otaian; Mount Harris Formation, Bluecliffs, Otaio River (type); foot of Mt Horrible, Pareora River, common.
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)