Benthonella Dall, 1889

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 : 338

Genus Benthonella Dall, 1889

Benthonella Dall, 1889: 281 .

TYPE SPECIES. — Benthonella gaza Dall, 1889: 282 , currently Benthonella tenella ( Jeffreys, 1869) , by original designation.

DIAGNOSIS. — Shell of small to medium size for the family, with transparent, colourless teleoconch; axial sculpture present, and spiral sculpture, when present, only on the base; protoconch multispiral with a low spire, finely keeled and coloured.

Pallial tentacles, eyes and posterior gland lacking.

REMARKS

Most of the species have both axial and spiral sculptures on the teleoconch and a slightly thickened labial varix, followed by a fragile and sharp edge, usually preserved intact only in freshly collected specimens. The umbilicus may be open, broad or narrow, or closed; sometimes the columellar lip may be expanded over the umbilical area, producing a false umbilical chink. For the description of the soft parts see Ponder (1985: 63) based on B. tenella , who addressed a very peculiar sperm duct opening to the kidney, and a possible renal copulation.We could not examine material of Benthonella =? loriei Weisbord,1962 , which is described as paucispiral ( Weisbord 1962: 129-130, pl. 46: figs 7-8, pl. 47: 6-7), and if confirmed, would represent the only known specie of Benthonella with non-planktotrophic development.

Some deep-water taxa, mostly described under the genus Rissoa Desmarest, 1814 , actually belong to Benthonella . For instance, Rissoa olangoensis Poppe, Tagaro & Stahlschmidt, 2015 from Philippines, off Olango Island in the Mactan Channel in front of Baring, 130 m depth, clearly belongs to Benthonella (see Poppe et al. 2015: 24, pl. 8, figs 1-3). It has, like the type species, a blunt, coloured protoconch with two peripheral keels and therefore, we propose Benthonella olangoensis ( Poppe, Tagaro & Stahlschmidt, 2015) as a new combination.

Pusillina kazakhstanica Amitrov, 2010 from the Oligocene of Kazakhstan, also belongs to Benthonella . Very similar to Benthonella lutetiana Lozouet, 2014 and to Benthonella priabonica Lozouet, 2014 , it essentially differs from both species for the presence on the protoconch of a thin median spiral keel vs 2 well spaced (one subsutural, the other suprasutural) in B. lutetiana and B. priabonica . Furthermore, the subsutural thickening of the axial ribs is stronger in B. lutetiana and B. priabonica . We propose Benthonella kazakhstanica ( Amitrov, 2010) as a new combination.

Hasegawa (2005) reported two distinct undescribed species belonging to Benthonella (as “ Alvania sp. ”and “ Benthonella sp. ” – Hasegawa 2005: 149, fig. 5I; 149, figs K, L).

We have found three species of Benthonella in French Polynesia, all undescribed: Benthonella boucheti n. sp., Benthonella basistriata n. sp., Benthonella communis n. sp.