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Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)

New Zealand Cenozoic Mollusca

Egotistica scirrhoma Marwick, 1934


(Pl. 21d): Bluecliffs, Otaio River, Otaian (Canterbury Museum)

Beu & Maxwell (1990): Chapter 11; p. 200; pl. 21 d.

Synonymy: Egotistica scirrhoma Marwick 1934, p. 17

Type species of Egotistica Marwick, 1934

Classification: Buccinulidae

Description: Rather small for subfamily (height 23-30 mm), cominelliform, spire half total height. Protoconch relatively large, mamillate, of 1.5 convex whorls, a few weak axial costellae near end, otherwise smooth. Teleoconch of 5 whorls, first whorl convex, later whorls prominently angled at or near middle, sutural ramp slightly concave; last whorl evenly convex from periphery to the short but rather thick, twisted neck. Axial sculpture of prominent, rounded costae with broad, concave interspaces, reaching from suture to suture at first but then becoming obsolete on upper part of ramp, extending across base of last whorl; 11-13 costae on penultimate whorl. Spiral sculpture commencing as 4 or 5 narrow, low cords, other spirals appearing by intercalation during growth, later whorls covered with prominent, crisp cords, most with interstitial threads, those on ramp mostly somewhat weaker than those below. Spirals finely crenulated by numerous growth lines. Aperture rather small, ovate, columella almost straight above, strongly twisted to left below, with a low, oblique ridge on twist. Siphonal canal short, strongly notched; fasciole prominent, of squarish section, margined above by a sharp ridge, below by a slightly less prominent ridge. Inner lip rather thickly callused, almost to end of canal; outer lip thin, weakly sigmoid, with a shallow indentation near anterior end, and bearing fine lirae within.

Comparison: Egotistica was proposed by Marwick (1934, p. 16) for buccinids with the teleoconch characters of Aethocola (sensu lato), but having a large, mamillate protoconch like that of Cominella rather than the small, conical protoconch characteristic of Aethocola. In fact, the short siphonal canal and the prominent, squarish fasciole set Egotistica apart from Aethocola (sensu stricto) and its subgenus Neocola, and suggest closer relationship to Nassicola (see above). Beu (1973b, p. 324) suggested that on the basis of its aperture, siphonal canal and fasciole, Nassicola could be more closely related to Cominella than to Austrofusus. Egotistica has a mamillate protoconch, and in this respect it is even more similar to Cominella and its relatives. However, in both Nassicola and Egotistica, but particularly in the former genus, the fasciole projects more strongly above the profile of the last whorl than in typical Cominella. This is, therefore, the other possible combination of characters in the Aethocola-Cominella complex: an analogue of Aethocola with a protoconch like that of Cominella, and there is no doubt that all these genera are closely related phylogenetically. Besides the two Otaian occurrences, Egotistica is recorded from the Mount Harris Formation at upper Tengawai River (Waitakian), and at Old Rifle Butts, Cape Wanbrow (Altonian), and from Muddy Creek, Gisborne district (Clifdenian; Marwick 1934, p. 17). All occurrences are in moderately deep-water (outer shelf or upper bathyal) siltstone, and species of Egotistica are rare at all localities.

Distribution: Otaian; Mount Harris Formation, Bluecliffs, Otaio River (type); Mt Horrible, Pareora River (rare).

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)


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