Benthonellania Lozouet, 1990

Amati, Bruno, Giulio, Andrea Di & Oliverio, Marco, 2022, Deep-water Rissoidae of the genera Benthonella Dall, 1889 and Benthonellania Lozouet, 1990 (Gastropoda, Caenogastropoda, Rissooidea) from French Polynesia, Zoosystema 44 (12), pp. 335-389 : 347-349

Genus Benthonellania Lozouet, 1990

Benthonellania Lozouet, 1990: 314 .

TYPE SPECIES. — Benthonellania gofasi Lozouet, 1990 by original designation.

DIAGNOSIS. — Shell of small to medium size for the family, with transparent, colourless teleoconch; axial sculpture present, spiral cords on the whole teleoconch or only on the base or rarely absent; protoconch slender with spiral cordlets, linear or zig-zag, and usually coloured when multispiral, with a low spire, smooth or with microgranules and colourless when paucispiral.

Pallial tentacles and eyes present and posterior gland well developed.

REMARKS

Benthonellania includes species with shell small to medium size, vitreous, colourless and with protoconch generally slender, coloured, with diversified sculpture, or smooth and colourless. For the soft parts see Lozouet (1990: 314); Gofas (1999: 95) (based on Benthonellania gofasi Lozouet, 1990 ). Benthonellania includes a group of species living from the lower continental shelf to bathyal depths. The type species is the Recent Eastern Atlantic B. gofasi , from Sénégal. Species fitting the shell features of Benthonellania are known in the Pleistocene of Nigeria and the Upper Miocene of Angola, and can be traced back to the Upper Oligocene of France ( Lozouet 1990: 313; 2014: 21). The genus as currently conceived, has a very wide geographic range, with 15 recognised species occurring in the Atlantic ( MolluscaBase 2021c) and one ( Rissoa aequatorialis Thiele, 1925: 84 , pl. 6, fig. 23) from the Indian Ocean, dubitatively suggested to belong to Benthonellania by Lozouet (1990: 326), or to Pusillina (Haurakia) by Ponder (1985: 30, as synonym of Rissoa africana Thiele, 1925 ).

Furthermore, several deep-water taxa originally introduced under other genera, probably belong to Benthonellania . For instance, the drawing of the holotype of Rissoa precipitata Dall, 1889 , from the Yucatan Strait, 1225 m depth (670 fms; more likely 1170 m [640 fms] as indicated in the MCZ Catalogue, and by Dall himself for other species from the Yucatan Strait), reported by Romer & Moore (1988: 133, fig. 5), does not match Dall’s original description and drawing ( Dall 1889: 279, pl. XIX, fig. 1) nor the holotype (MCZ-Mala–7470) ( Figs 6 A-D). It is very similar to e.g. Benthonellania agastachys Bouchet & Warén, 1993 , and we accordingly propose Benthonellania precipitata ( Dall, 1889) as a new combination for Rissoa precipitata Dall, 1889 .

Alvania colombiana Romer & Moore, 1988 , from the western Atlantic Ocean ( Colombia, Florida, Puerto Rico, Brazil, 45-261 m depth) was originally compared with some species currently in Benthonellania ( Romer & Moore 1988: 131-133; figs 1, 2). It was kept in Alvania by Absalão & Santos (2004: 338) and Da Silva (2012: 48), but a placement in Benthonellania was suggested by Moolenbeek & Faber (1991: 51) and Oliver & Rolán (2017: 48), a view on which we agree. Oliver & Rolán (2017: 50) synthetically redescribed the apex as “[…] smooth multispiral protoconch except for the presence of a conspicuous suprasutural spiral cord which tends to be undulating in zig-zag”, and we add that there is also a subsutural series of microgranules. Based on all these features (including also the light brown protoconch and the sculpture of the teleoconch), we, thus, propose Benthonellania colombiana ( Romer & Moore, 1988) as a new combination for Alvania colombiana Romer & Moore, 1988 .

Rissoa profundior Hedley, 1907 , was described from 33 miles east of Sydney (c. 1458 m depth), and is currently classified in the genus Haurakia after Cotton (1944: 294). Rissoa profundior is very similar to Benthonellania charope ( Melvill & Standen, 1901) and Benthonellania antepelagica Lozouet, 1990 , in its very scalariform profile, robust crown and deep subsutural groove, robust axial sculpture and weaker spiral one more evident on the base ( Hedley 1907: 358, pl. LXVII, fig. 15; Lozouet 1990: 319). Thus, we propose Benthonellania profundior ( Hedley, 1907) as a new combination for Rissoa profundior Hedley, 1907 .

Rissoa sumatrana Thiele, 1925 ( Thiele 1925: 84, pl. 6, fig. 25), from Siberut Island ( Indonesia, Indian Ocean) 750 m depth, has the typical slender profile of Benthonellania and the crown of small tubercles at tip of axial. Thus, we propose Benthonellania sumatrana ( Thiele, 1925) as a new combination for Rissoa sumatrana Thiele, 1925 .

Additionally, we propose to move Rissoa hertzogi Thiele, 1925 , Rissoa africana Thiele, 1925 and R. aequatorialis Thiele, 1925 into Benthonellania (three new combinations, see below). Within the type material of Rissoa africana Thiele, 1925 (see below), 199 shells from East Africa (off Somalia) clearly represented a distinct undescribed species, that we describe here as Benthonellania thielei n. sp.

Alvania waisiuensis Beets, 1942 ( MolluscaBase 2021d), from the Upper Oligocene of Indonesia, has a paucispiral protoconch ( Lozouet 1990: 319), and a teleoconch with ornamentation and profile resembling a typical Benthonellania . However, the poor original description and iconography alone ( Beets 1942: 269-270; pl. 27, figs 41-42) are not sufficient for a conclusive classification ( Lozouet 1990: 319). Therefore, pending examination of the types and/or new material, we refrain from proposing a formal new combination for this species.

Hasegawa (2005) reported an undescribed species of Benthonellania (“ Benthonellania sp. ” – Hasegawa 2005: 149, fig. 5J) from Japan.

Nine Recent species (out of 27), Benthonellania fayalensis (R. B. Watson, 1886) , B. oligostigma Bouchet & Warén, 1993 , B. agastachys Bouchet & Warén, 1993 , B. profundior n. comb., B. charope , B. hertzogi Thiele, 1925 n. comb., B. thielei n. sp. and B. africana n. comb., and the fossil B. antepelagica have a paucispiral protoconch with weak or no sculpture. Among the species with multispiral protoconch, several show spiral zig-zag cordlets, a pattern that is not unusual in various – sometimes unrelated – rissoid lineages, as already noted by Oliver & Rolán (2017).

We have found seven undescribed species of Benthonellania in French Polynesia: Benthonellania bouteti n. sp., Benthonellania alis n. sp., Benthonellania tarava n. sp., Benthonellania megan n. sp., Benthonellania tuamotu n. sp., Benthonellania lozoueti n. sp. and Benthonellania maestratii n. sp. and one in the Western Indian Ocean Benthonellania thielei n. sp.

Figures

FIG. 6. — Benthonellania precipitata (Dall, 1889) n. comb.: A-D, holotype (MCZ–7470), height 3.92 mm; D, detail of the first whorls; E, relevant page of the Catalogue of Mollusca in the Museum of Comparative Zoology (photo by Alana Rivera). Scale bar: D, 0.25 mm.