Palaina ascendens (Mousson, 1870) Mousson, 1870

Neubert, Eike & Bouchet, Philippe, 2015, The Diplommatinidae of Fiji - a hotspot of Pacific land snail biodiversity (Caenogastropoda, Cyclophoroidea), ZooKeys 487, pp. 1-85 : 35-38

Taxon classification Animalia Mesogastropoda Diplommatinidae

Palaina ascendens (Mousson, 1870) comb. n. Figs 72-73

Diplommatina ascendens Mousson 1870, Journal de Conchyliologie, 18: 184, pl. VIII, fig. 5. Type locality: "Ile de Viti-Levu".

Diplommatina (Pseudopalaina) ascendens , - Kobelt 1902, Cyclophoridae : 451.

Type material.

The 2 specimens originally mentioned by Mousson could not be traced in the collection of Mousson in Zurich nor in the collection of the Journal de Conchyliologie in Paris. In a lot in ZMZ, however, originally identified by Mousson as " Diancta martensi ", a specimen similar to the - somewhat sketchy - original illustration of Diancta ascendens is present. This specimen cannot be considered type material, because it was acquired by Mousson in his collection in 1872, i.e. two years after the description of the species. To stabilize the use of the name, this specimen is here selected as neotype. Neotype: ZMZ 526689d, here designated, Viti Levu, “Tatatan”, coll. Mousson ex Graeffe 1872 (Fig. 72). The locality “Tatatan” could not be identified with certainty; possibly it is Cautata, NE of Suva.

Original description.

"T. sinistrorsa, longe rimata, acute ovata, lamellosocostulata, carneo-albescens. Spira convexo-conica; summo obtusulo, graniformi; sutura subprofunda. Anfr. 5 1/2, celeriter accrescentes, convexi; nucleolares laevigati; sequentes ventrosi, lamelliferi; penultimus in ventre retractus et compressus, tenuiter costulatus, lateraliter ruga transversa proeditus; ultimus attenuatus, lente et valde usque ad suturam anfr. tertii fere ascendens, ad rimam paulo impressus. Apert. tangentialis, sursum versa [40° cum axi], transverse perobliqua, subpatula, intus et extus obtuse quadrata. Perist. subexpansum, antice duplicatim incrassatum; marginibus convergentibus, lamina sinistrorsa junctis; columellari et externo supra antrorsum productis, infra sinuatis. Columella obtuse nodulata, interdum lamina producta circumdata. - Long. 3,8, diam. 2,2 mill. - Rat. anfr. 5: 1. - Rat. apert. 5: 4. Hab. Ile de Viti-Levu."

Diagnosis.

Shell whitish, moderately large bulb, sculpture of widely spaced ribs, aperture subquadrate, with two denticles.

Description.

Shell sinistral, medium sized, oval, whitish; protoconch acute, granulated; last whorl not constricted with a moderately large bulb; last whorl strongly ascending; teleoconch sculpture of coarse widely spaced ribs; umbilicus slit-like, periomphalum narrow; aperture subquadrate, peristome reinforced by a lip, with two denticles on each side (Fig. 73, arrows), broadly attached to last whorl; no pleats visible in the aperture; internal lamellar system not studied.

Operculum unknown.

Measurements.

Neotype (Fig. 73): H = 3.31; D = 2.13; PH = 1.32; PD = 1.40; W = 5.

Distribution.

Uncertain.

Remarks.

The lot ZMZ 526689 contained a larger number of Diancta martensi (ZMZ 526689c), but also one specimen of Palaina tuberosa (ZMZ 526689a) and a specimen of Palaina latecostata (ZMZ 526689b).

Diplommatina ascendens is here classified in Palaina because it has a well-developed bulb. It is unmistakable by the formation of the aperture: usually, species of Palaina have a rounded aperture, and not a subquadrate oblique aperture, which is probably why Mousson may have merged it with the superficially similar Diancta martensi . However, the latter is a true species of Diancta as evidenced by the lack of a bulb and the internal lamellar system.