Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 22f): GS9700, J38/f9681, Sutherlands, Tengawai River, South Canterbury, Altonian (GNS)
Beu & Maxwell (1990): Chapter 11; p. 213; pl. 22 f.
Synonymy: Turbinella brevirostris Hutton 1877b, p. 596; Peristernia brevirostris; Latirus brevirostris; Leucozonia brevirostris; Bivetia (?) brevirostris
Type species of Maorivetia Finlay, 1924
Classification: Cancellariidae: Cancellariinae
Description: Moderately large for family (height 35-50 mm), broadly ovate, spire 0.3-0.4 total height. Protoconch prominent, mamillate, of 1.5 smooth whorls, initial whorl inrolled. Teleoconch of 4-5 whorls, first whorl or so convex, but later whorls typically turned in towards suture to form a narrow sutural shelf. Last 1-1.5 whorls with a prominent subsutural fold with a concave zone below, thereby greatly accentuating sutural shelf; periphery of last whorl strongly convex, excavated below with a short, broad neck. Axial sculpture on first 2-3 whorls of growth lines only, prominent rounded costae appearing on 3rd or 4th whorl, reaching from suture to suture on spire and nodulose on sutural shelf, typically extending across base almost to fasciole on last whorl; 13-15 costae on last whorl. Spiral sculpture commencing as about 8 narrow, low, closely spaced cords, additional cords and threads appearing during growth, sutural shelf on last whorl smooth or only feebly sculptured, remainder of whorl covered with numerous cords (typically longitudinally grooved) and threads, coarser spirals often somewhat thickened where they cross axial costae. Aperture ovate, constricted posteriorly to form narrow channel; columella vertical, twisted to left near anterior end to form short, obliquely notched siphonal canal, bearing 2 prominent plaits posteriorly, some shells with short ridge on twist as well. Fasciole rounded, strongly protruding. Inner lip prominently callused, some shells with a few weak, irregular ridges near columellar plaits. Outer lip thin, lirate within.
Comparison: Maorivetia brevirostris varies considerably in spire height and sculpture and in the prominence of the sutural ramp; in particular, subadult shells may look very different from adults because of the late development of axial costae and because the sutural ramp is far less prominent on early whorls. It is unlikely to be confused with any other New Zealand cancellariid (but see discussion under Aphera scopalveus, below). The only other species of similar size is Scalptia christiei (Pl. 15l), which differs in being taller-spired, in having a channelled sutural ramp, in its narrower, more strongly prosocline costae and in having the columella slightly but distinctly deflected to the right. Maorivetia is monotypic and of uncertain affinity. There is some resemblance to Sydaphera Iredale, 1929, but species assigned to that genus have three rather than two columellar plaits.
Distribution: Altonian; Southburn Sand, White Rock River (type); Sutherlands; Target Gully Shellbed; Ardgowan Shellbed; Mount Harris Formation, Awamoa Creek; Dyer's Run, Waihao Valley; Mount Brown Formation, Weka Pass.
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)