Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 22p): GS9685, J41/f9499B, Pukeuri road cutting, Oamaru, Altonian (GNS)
Beu & Maxwell (1990): Chapter 11; p. 212; pl. 22 p.
Synonymy: Drillia (Crassispira) costifer Suter 1917, p. 48
Classification: Turridae: Borsoniinae?
Description: Small for subfamily (height 7-8 mm), narrowly fusiform, spire 0.6 total height. Protoconch mamillate, of 1.5 smooth whorls. Teleoconch of about 5 whorls, shouldered near middle on spire; sutural ramp concave, some shells with weak subsutural swelling; last whorl weakly excavated. Axial sculpture of narrow, opisthocline costae with much broader interspaces, reaching from shoulder angle to lower suture on spire, typically obsolete on ramp, but represented by small nodules just below suture on some shells. Costae weaker on last whorl of most specimens, scarcely extending onto base, reduced to short peripheral nodules on some shells; 12-15 costae on penultimate whorl. Spiral sculpture weak, obsolete on spire of some shells, typically discernible only on base and particularly on neck of last whorl, consisting of low, narrow cords. Aperture narrow; siphonal canal only weakly differentiated, shallowly notched. Inner lip thinly callused, no parietal callus pad. Outer lip thin, with shallow U-shaped anal sinus, its apex near middle of ramp.
Comparison: Mauidrillia costifer is distinguished from other species of the genus by its prominently angled whorls, its relatively prominent axial costae and its weak spiral sculpture. Mauidrillia ranges from Duntroonian to Tongaporutuan (and possibly to Waipipian) in New Zealand, and from Late Eocene to Miocene in Australia. The genus was particularly speciose in the Early Miocene; eight species have been described from Otaian and Altonian beds in North Otago and South Canterbury. Considerable care is needed when trying to identify these small turrids, particularly as two or more species occur together at some localities (e.g., Pukeuri and Awamoa Creek) (see Powell 1942, pp. 85-87). Although some species (e.g., the Duntroonian M. cinctuta) seem to have lived in a shallow-water habitat, most records of Mauidrillia are from mid- to outer shelf faunules, and a few are from upper bathyal assemblages. Mauidrillia has long been assigned to the family Drilliidae, but the absence of a parietal callus pad, and the general resemblance (except for the absence of columellar plaits) to some species of Borsonia indicate referral to the Borsoniinae (Maxwell 1988a, p. 63). Of course, reassessment of this position will be part of the on-going rethinking of conoidean phylogeny.
Distribution: Altonian; Mount Harris Formation, Pukeuri road cutting, Oamaru (type); Awamoa Creek, moderately 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)