Pseudolibera solemi, 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 : 42-44

Pseudolibera solemi sp. nov.

Figures 25 A; 26; 36I; 38A; 39.

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

Examined material (114 specimens). Holotype: MNHN 25590, Mk16. Paratypes: MNHN 25591, 8 shells, Mk16. Additional material: MNHN, unregistered, 3 shells, one of which gold coated, “ Pseudolibera makateaensis n.sp. (undescribed by A. Solem) #1”; 17 shells, Mk04; 13 shells, Mk12; 1 shell, Mk13; 10 shells, Mk16; 6 shells, Mk19; 8 shells, Mk21; 47 shells, Mk22.

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 8 mm in diameter, depressed to subdepressed, flammulated; apex barely to strongly raised, spire elevated; peripheral keel short and blunt; teleoconch sculptured by subequal axial and spiral ribs, very slightly reduced on shell base; palatal wall devoid of barriers; 1 parietal barrier extending 3/4 to 2 whorls, not bifurcated.

Description. Shell depressed to subdepressed, dome-shaped to trigonal, white, with regularly spaced, amber flammulations on the shell periphery, tapering apically, usually absent on shell base; commonly with a fawn to light orange background coloration and a maroon tint on the last whorl. Shell wall thin, opaque to subpellucid; periostracum adherent, shiny. Apex barely to strongly raised; spire elevated, latter whorls descending more rapidly. Apical suture shallowly impressed at apex, progressively deepening in subsequent whorls; umbilical suture adpressed. Whorls gently concave above and below relatively short, blunt peripheral keel, transitioning into broadly convex toward the apical suture and shell base; junction of basal and columellar walls initially obtusely angled, developing a keel approximately from the fourth whorl onwards. Transition between protoconch and teleoconch indistinct. Primary axial sculpture of the protoconch composed of low, narrow ribs, with interspaces two to four times their width; two to four secondary axial riblets, each approximately half the width of the primary ribs and wavy in morphology, occupying the interspaces between primary ribs. Primary ribs of the protoconch gradually transitioning into broader and taller ribs, which comprise the primary axial sculpture of the teleoconch; secondary riblets of the protoconch gradually increasing in number and persisting as the secondary axial sculpture of the teleoconch. Spiral sculpture developing approximately from the third whorl onwards, composed of wavy ribs, more closely spaced and slightly lower than the primary axial ribs of the teleoconch; nodular projections present at intersections between spiral and axial ribs. Axial sculpture very slightly reduced on shell base. Umbilicus rapidly expanding in diameter for approximately the first 3 whorls, remaining constant in diameter for approximately 1 whorl, subsequently constricted by inward growth of the lower columellar wall and lip. Peristome elongated crescent, with rostrate periphery; 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, varying in length from approximately 3/4 to 2 whorls. Other shell features that can be expressed numerically are shown in Table 3.

Remarks. A lot labelled as “ Pseudolibera makateaensis n.sp. (undescribed by A. Solem) #1” in the collections of the MNHN indicates that P. solemi is one of three undescribed species Solem (1983) recognized among the material Aubert de la Rüe & Soyer (1958) had erroneously reported as Trochonanina obconica . The lot contained two specimens, one of which gold coated; to these we added one shell with the same presumed origin that Solem had misidentified as P. lillianae . Solem (1983, p. 280) cited his study of the three undescribed species as “in preparation”, but a search for his unpublished manuscript in the archives of the FMNH proved unfruitful (J. Gerber, personal communication 2012). Analysis of these specimens and numerous matching shells collected in 2005 revealed that they indeed represent a new species.

P. solemi displays considerable variation in the prominence and length of its apertural barrier. In at least two of the specimens studied by Solem and in six from the type locality (station Mk16) the barrier extends posteriorly for more than 1 whorl from the peristome and, at its highest point, reaches approximately half the height of the aperture. The barrier was found to extend for approximately 2 whorls in one of these individuals ( Fig. 26 D), but 1.5 whorls seems more typical. In specimens collected elsewhere, the apertural barrier appears to reach only half the height recorded at Mk16, and to vary between 0.75 and 1 whorl in extension, with the latter configuration more frequent. P. solemi is also somewhat variable in the elevation of its apex and spire. Specimens with a lower spire approach the shape of P. lillianae , but they may be distinguished from that species by a smaller shell size at the same number of whorls, shorter and less acute peripheral keel, flammulations more spaced and restricted to the shell periphery, and by more prominent sculpture on the shell base. With further study and additional material, P. solemi may prove to be a complex of similar species differing only in details of shell shape and morphology of the apertural barrier. At present regional differences seem too small and complex to warrant formal recognition.

Etymology. This species is dedicated to Alan Solem, who first recognized this species and whose monographs on endodontids have provided the foundation for all subsequent studies of the family.

Figures

FIGURE 25. Holotypes of: A. Pseudolibera solemi sp. nov.; B. P. matthieui sp. nov.; C. P. cookei sp. nov.; D. P. aubertdelaruei sp. nov. Scale bars = 5 mm.

FIGURE 26. Pseudolibera solemi sp. nov. A – C. Holotype (MNHN 25590), apical views; A. General view; B. Sculpture of the protoconch and early teleoconch; C. Sculpture of the late teleoconch; D. Umbilical view of specimen from station Mk 16, showing the apertural barrier extending posteriorly for more than one whorl. Scale bars: A, D = 2 mm; B, C = 0.4 mm.