Palaina Semper, 1865

Neubert, Eike & Bouchet, Philippe, 2015, The Diplommatinidae of Fiji - a hotspot of Pacific land snail biodiversity (Caenogastropoda, Cyclophoroidea), ZooKeys 487, pp. 1-85 : 34-35

Taxon classification Animalia Mesogastropoda Diplommatinidae

Palaina Semper, 1865

Palaina Semper 1865a, Journal de Conchyliologie, 13: 291, 292. Type species: Diplommatina macgillivrayi Pfeiffer, 1854 [from Lord Howe Island], by subsequent designation of Iredale (1944: 303). Thiele (1929: 109) and Wenz (1939: 481) cited " Palaina patula Crosse" as type species, but this was a nomen nudum in 1865, later published as Palaina patula Semper, 1866.

Macropalaina Möllendorff 1897, Nachrichtsblatt der deutschen malakozoologischen Gesellschaft, 29: 43. Type species: Diplommatina pomatiaeformis Mousson, 1870, by original designation.

Diagnosis.

Shell elongate oval, last whorl not constricted, usually with a bulbous last whorl, aperture in a rather central position in relation to the shell longitudinal axis, without apertural dentition; internal dentition mainly concerns formation of the columellaris, which may be toothed to completely unarmed; operculum with or without concentric lamellae; with a low arcuate ridge on the inner surface.

Semper established the name Palaina without providing a description. Kobelt’s (1902: 394) definition is undiagnostic, as this author included under this header many species from the Pacific diplommatinid radiation, which can be considered a polyphyletic assemblage: "Shell ovate cone-shaped, in most cases sinistral, with a diverse sculpture. Last whorl constricted at the beginning or the first quarter; aperture without teeth, operculum deeply sunken, uncalcified, circular, with several whorls. Shell elongate oval; no dentition; operculum corneous, with thick concentric ridges" [translated from German].

A re-definition of Palaina was provided by Yamazaki et al. (2013: 16), who considered Eupalaina Kobelt & Moellendorff, 1898 as a subgenus of Palaina (subsequent type designation Palaina patula Crosse, 1866). The type species of Palaina is Diplommatina macgillivrayi Pfeiffer, 1854, from Lord Howe Island, from which island several species of Palaina are recorded ( Stanisic et al. 2010). Comparing their shells to those from Palau and to those from Fiji that we include in Palaina , they differ by their quite compact and stout outline (the Fiji species are more variable in shape). The inner lamellar system of the Lord Howe radiation is unknown. However, Tillier (1981) illustrated the operculum of Palaina macgillivrayi , which seems to have a bilobed ridge on the inner surface, and thus differs from what is seen in the Palau species, which have a single strong ridge ( Yamazaki et al. 2013: Figs 10 A–D), and in the Fiji species, which have a low, inconspicuous rigde. In shell shape and formation of the opercula, the Fiji " Palaina " are close to those from New Caledonia, but unfortunately, Tillier (1981) did not investigate the internal lamellar system in the latter, so potentially useful information is lacking. The species in the New Caledonia radiation have no penis, while the Palau species possess one. Yamazaki et al. (2013) claimed that Tillier (1981) found Palaina macgillivrayi to also have no penis, a statement that, however, is not explicit in Tillier’s text. For Fiji, no information is available in this regard at present. This short review shows that knowledge of this group is patchy. It seems possible that all the different island radiations will have to be separated at the generic level once the full set of characters is known. For the time being, we conservatively apply Palaina in a broad sense to the Fiji radiation, although we anticipate a separation at the generic level (for which the name Macropalaina is available) from the Lord Howe and Palau radiations The Fiji species might not even be monophyletic.