Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 8s): GS9508, J40/f8803, McCulloch's Bridge, Kaiatan (GNS)
Beu & Maxwell (1990): Chapter 8; p. 120; pl. 8 s.
Synonymy: Exilia waihaoensis Suter 1917, p. 25; Zexilia waihaoensis; Z. tenuilirata Laws 1935b, p. 26; Z. submarginata Laws 1935b, p. 26
Type species of Zexilia Finlay, 1927, a synonym of Exilia Conrad, 1860 (Maxwell 1988a, p. 53; Kantor et al. 2001, p. 87)
Classification: Turbinellidae (not Ptychatractidae; Bouchet et al. 2005, p. 256)
Description: Size moderate for genus (height 25-40 mm), narrowly fusiform, spire about half total height. Protoconch narrowly dome-shaped, of about 3 whorls with weak, arcuate riblets on last 0.25 whorl. Teleoconch of up to 9.5 whorls, spire whorls lightly convex or flat-sided, some shells with weak subsutural swelling; last whorl contracted gradually, with a long, straight, slender neck. Axial sculpture of narrow, rounded, gendy flexuous costae, reaching from suture to suture on spire whorls, dying out on base of last whorl; 12-20 on penultimate whorl. Spiral sculpture highly variable, some shells with prominent, strap-like lirae, others with much weaker, rounded cords with narrow, even linear interspaces; 5-10 on spire whorls, numerous additional spirals of variable strength on base and neck. Adapical spiral often stronger than others, situated on subsutural swelling and weakly nodulated at intersections with axial costae. Other cords crossing costae without change except for slight thickening. Aperture elongate-pyriform; siphonal canal long, slender; columella straight or with a weak twist above middle. Inner lip slightly impressed adapically, thinly callused below; outer lip thin, flexuous with a broad, shallowly arcuate sinus on upper third.
Comparison: Exilia waihaoensis differs from younger New Zealand species of Exilia in its relatively large size and prominent axial sculpture, and by having a dome-shaped protoconch of about three whorls rather than a mamillate one of about 1.5 whorls. E. waihaoensis is highly variable, and Maxwell (1992, pp. 131-132) included Zexilia tenuilirata and Z. submarginata in its synonymy, suggesting that it also includes E. crassicostata (probably Kaiatan, Waihao River) and Zexilia hampdenensis (Bortonian, Hampden Beach).
Exilia ranges from Wangaloan to Waiauan in New Zealand; elsewhere it is recorded from Late Cretaceous to Recent (Bentson 1940; Kantor et al. 2001). Most New Zealand occurrences are from mid-outer shelf or upper bathyal assemblages. Although long considered to belong in the Fasciolariidae, Exilia was transferred to the Turbinellidae by Maxwell (1988a, p. 53) and Kantor et al. (2001), and Kantor et al. (2001) synonymised the Recent genus Benthovoluta with Exilia. They also described the new Recent species E. kiwi from the Bounty Trough and Mernoo Bank, east of the South Island, in 1386-1676 m, and transferred Chathamidia expeditionis Dell, 1956 (off eastern South Island to the Chatham Islands, in 476-984 m) to Exilia.
Distribution: Bortonian-Kaiatan; Waihao Greensand, McCulloch's Bridge, Waihao River, Kaiatan (type locality of all three nominal species); Waihao Downs; Kapua Tuff, Waihao River; Kaiata Formation, Point Elizabeth Beach, Westland. Not uncommon at McCulloch's Bridge, rare at other 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
(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)