Provanna sp.

Amano, Kazutaka & Little, Crispin T. S., 2014, Miocene abyssochrysoid gastropod Provanna from Japanese seep and whale-fall sites, Acta Palaeontologica Polonica 59 (1), pp. 163-172 : 167-170

Provanna sp.

Fig. 4 .

2007 Provanna ? sp.; Amano et al. 2007: fig. 3A, B.

Material.— Two specimens from the whale-fall site of the Middle Miocene Nupinai Formation , eastern Hokkaido, Japan .

Measurements.—See Table 4.

Description. —Shell small, up to 5.0 mm high, ovate fusiform; teleoconch with three whorls; protoconch not preserved. Suture very shallow; whorl side curved without shoulder. Surface ornamented by distinct axial ribs and spiral cords, forming cancellate sculpture at crossing points. Axial ribs almost straight, numbering 13 on penultimate whorl and 16 on body whorl. Four spiral cords on penultimate whorl and eight on body whorl.

Remarks. —There are three Provanna species with cancellate ornament that can be compared to the Rekifune species. However, two of these ( P. admetoides Warén and Ponder, 1991 and P. marshalli Saether, Little, and Campbell, 2010 ) have distinct tabulated shoulders, lacking in the Rekifune species, and one ( P. nassariaeformis Okutani, 1990 ) has a wider body whorl than seen in either of the Rekifune specimens.

We do not name this species at present because we have only two specimens, and these are present as external moulds only. Amano et al. (2007) illustrated these specimens as Provanna ? sp., but small gastropods having such cancellate sculpture recorded from chemosynthetic communities can be also be found amongst the nassariids, cancellariids, and turrids. However, we are confident that the Rekifune specimens do not belong to these families for the following reasons. The lack of a fasciole and folding on the aperture inner lip suggests the Rekifune specimens are not nassariids, and collumellar folds, which are characteristic of the cancellariids, are also lacking in the Rekifune specimens, indicating they do not belong to this family either. Further, species of top of aperture where it meets the body whorl wall. C. Topotype, JUE 15906-1, fractured apical whorl shell, white arrows indicate relict crossed lamellar structures in the innermost layer. D. Paratype, JUE 15905-1, fractured apical whorl shell. E. Provanna hirokoae sp. nov., paratype, 15902-4, fractured body whorl shell. Abbreviations: cl, crossed lamellar layer;?cl, possible crossed lamellar layer; p, periostracum; spl, simple prismatic layer.

the nassariids and cancellariid are rare in the modern chemosynthetic fauna. The Rekifune specimens lack the posteriorly situated growth lines which characterize the turrids.

Figures

Fig. 4. Abyssochrysoid gastropod Provanna sp., Middle Miocene Nupinai Formation (locality 2). Silicone rubber moulds coated with ammonium chloride. A. JUE 15846-1, apertural view. B. JUE 15846-2, adapertural oblique view.