Pseudolibera extincta, Sartori, André F., Gargominy, Olivier & Fontaine, Benoît, 2014

Sartori, André F., Gargominy, Olivier & Fontaine, Benoît, 2014, Radiation and decline of endodontid land snails in Makatea, French Polynesia, Zootaxa 3772 (1), pp. 1-68 : 50

Pseudolibera extincta sp. nov.

Figures 30 A; 31; 36F; 38C; 39.

Trochonanina obconica (Pease) [in part]—Aubert de la Rüe & Soyer 1958, p. 365, non Helix obconica Pease 1865 .

Examined material (30 specimens). Holotype: MNHN 25592, Mk16. Paratypes: MNHN 25593, 8 shells, Mk16. Additional material: MNHN, unregistered, 3 shells, one of which gold coated, “ Pseudolibera depressa n.sp. (undescribed by A. Solem) #4” [collected by E. Aubert de la Rüe in 1955 in Makatea; see remarks below]; 15 shells, Mk16; 3 shells, Mk12.

Type locality. Road descending to Temao, Makatea (15.82593°S; 148.27534°W). Lower side of the road below rocks. Limestone, alt. 10 m; station Mk16.

Diagnosis. Shell less than 7 mm in diameter, depressed, flammulated; apex depressed, spire elevated; peripheral keel upturned; teleoconch sculptured by crowded axial ribs (> 150 ribs on body whorl) and spiral lirae, not reduced on shell base; palatal wall devoid of barriers; 1 parietal barrier extending 1½ whorls, not bifurcated.

Description. Shell depressed, dome-shaped, white, with regularly spaced, amber flammulations on the apical surface, absent on the shell base. Shell wall thin, opaque to subpellucid; periostracum adherent, shiny. Apex and first 2½ whorls depressed; spire elevated; later whorls descending progressively more rapidly. Apical suture shallowly impressed at apex, gradually transitioning to adpressed by the end of the third whorl, progressively deepening from the fourth whorl onwards; umbilical suture impressed at apex, adpressed approximately from the fourth whorl onwards. Whorls sharply concave immediately above upturned peripheral keel, forming a welldefined groove between keel and supraperipheral wall; broadly convex from the apical suture to the vicinity of the groove. Shell base broadly convex, transitioning into gently concave in the vicinity of the peripheral keel; junction of basal and columellar walls initially obtusely angled, developing a keel approximately from the fifth whorl onwards. Transition between protoconch and teleoconch indistinct. Protoconch sculptured by fine axial riblets, with interspaces c. 2–3 times their width, and by minute spiral lirae, with interspaces c. 1–3 times their width. Axial riblets of the protoconch gradually transitioning into broader and taller ribs, which comprise the primary axial sculpture of the teleoconch. Secondary axial sculpture of the teleoconch composed of minute lirae, with interspaces approximately equal to their width. Spiral lirae of the protoconch persisting on the surface of the teleoconch, forming tiny nodules at intersections with axial lirae. Sculpture not reduced on shell base. Umbilicus rapidly expanding in diameter for approximately the first 3 whorls, remaining constant in diameter for approximately 2 whorls, subsequently constricted by inward growth of the lower columellar wall and lip. Peristome subquadrate; columellar lip reflected. Palatal wall devoid of barriers. Parietal wall with 1 barrier, positioned slightly closer to the apical than the umbilical suture, descending gradually anteriorly and posteriorly, extending for approximately 1½ whorls. Other shell features that can be expressed numerically are shown in Table 3.

Remarks. P. extincta is one of three undescribed species Solem recognized among the material Aubert de la Rüe & Soyer (1958) erroneously reported as Trochonanina obconica (see remarks under P. solemi for details). It is easily distinguished from other Pseudolibera by its depressed apex, upturned peripheral keel and teleoconch sculpture of crowded, low axial ribs and much reduced spiral lirae.

Etymology. From extinctus (Latin), in reference to the fate of much of the native endodontid fauna of Pacific islands.

Figures

FIGURE 30. Holotypes of: A. Pseudolibera extincta sp. nov.; B. P. paraminderae sp. nov.; C. P. elieporoii sp. nov.; D. P. parva sp. nov. Scale bars: A – C = 5 mm; D = 3 mm.