Pisinna Monterosato, 1878

Absalão, Franklin Noel Santos Ricardo Silva, 2004, First record of the genus Pisinna Monterosato, 1878 (Mollusca, Gastropoda, Anabathridae) from the southwest Atlantic, with description of a new species, Zootaxa 723, pp. 1-6 : 2-3

Genus Pisinna Monterosato, 1878

Type species: Rissoa punctulum Philippi, 1836 , subsequent designation by Cossmann, 1921: 33. Recent, Mediterranean Sea (Figs. 25F, G; 26F, G).

Diagnosis (adapted from Ponder: 1983, 1998): Shell pupoid­elongate, without umbilicus. Teleoconch smooth or with axial or spiral sculpture. Protoconch paucispiral, domeshaped, sculptured with minute pits arranged in spiral lines. Aperture usually circular to oval, with peristome single or double. Varix usually present on the outer lip. Operculum oval, corneous, with two layers, eccentric nucleus, peg usually absent, or small when present; longitudinal cord absent, may have one thread around the margin.

Remarks: According to Ponder (1983), eight genera are recognized in the Anabathridae . The genera are mainly (but not exclusively) distinguished on shell and operculum characters. Although we have not seen soft parts, in our opinion the shell profile and protoconch morphology strongly suggest the appropriate generic placement according to Pon­ der & Yoo (1976: 154). Among the genera of Anabathridae of the Atlantic, Nodulus Monterosato, 1878 and Afriscrobs Ponder, 1983 can be distinguished by their protoconchs. Nodulus shows rather irregular pits, the surface sometimes raised into weak irregular wrinkles, while Afriscrobs has protoconchs with exceedingly minute puncta not arranged in spiral rows.

All other genera, i.e., Anabathron Frauenfeld, 1867 , Amphithalamus Carpenter, 1864 , Microdryas Laseron, 1950 , Badepigrus Iredale, 1955 , Pseudestea Ponder, 1967 and Pisinna share the same type of dome­shaped protoconch and the spiral rows of pits. P. bicincta n.sp. does not conform to Microdryas , because the latter has conspicuous spiral ornamentation on the teleoconch; neither does it fit in any of the other four genera, because all of them have the inner lip separated from the parietal wall, projecting the peristome forwards.

This pattern is very constant in Pisinna: Ponder & Yoo (1976: 164, 166, 168, 172, 175, 181, 183, 184, 184, 186, 187), respectively, showed that the following species share with P. bicincta n.sp. exactly the same protoconch pattern: P. albizona (Laseron, 1950) , P. approxima (Petterd, 1884) , P. b i c o l o r (Petterd, 1884), P. columnaria (Redley & May, 1908), P. flindersii (Woods, 1877) , P. kershawi (Woods, 1878) , P. l a s e ro n i Ponder & Yoo, 1976, P. megastona Ponder & Yoo, 1976 , P. moretonensis Ponder & Yoo, 1976 , P. o b l a t a (Laseron, 1956), P. olivacea (Frauenfeld, 1867) . If we consider these taxa as a valid sample of the protoconch morphology in Pisinna , we conclude that P. bicincta n.sp. cannot be excluded from this genus. Although most of the species of Pisinna have a reddish protoconch, in P. bicincta n.sp. the protoconch is orange. In view of the variability in shell profile and sutures, no patterns can be defined.

The only genus of Anabathridae previously reported from Brazil is Amphitalamus , which has a wide umbilicus (Rios 1994) and can be easily distinguished from Pisinna which lacks an umbilicus. The concentration of members of the genus Pisinna around the Australian Region, and the location of its type species ( Rissoa punctulum ) in the Mediterranean Sea, raises an intriguing question about the origin of this taxon. Ponder & Yoo, 1976:152 suggested “that the genus had its origins in the temperate Australian area (probably New Zealand) and then spread widely through the Indo­Pacific and to the Mediterranean via the Tethys Sea. It is, however, also possible that Pisinna evolved in the early Tertiary Tethys Sea and then migrated southwards, followed by a spectacular speciation in the temperate waters of Australasia.” In our opinion, no hypothesis is adequately supported by current data. Although no previously known species has filled the geographical gap between the Mediterranean Sea and the Australian Region, as P. bicincta n.sp. now begins to do, we must wait for more detailed knowledge about phylogeny and geographic distribution in order to form a confident hypothesis of the origin of the genus Pisinna .

Although we acknowledge that the generic assignment of this new species is not completely firm, including it in Pisinna is the best option.