Minidonta bieleri, Sartori, André F., Gargominy, Olivier & Fontaine, Benoît, 2013

Sartori, André F., Gargominy, Olivier & Fontaine, Benoît, 2013, Anthropogenic extinction of Pacific land snails: A case study of Rurutu, French Polynesia, with description of eight new species of endodontids (Pulmonata), Zootaxa 3640 (3), pp. 343-372 : 363-365

Minidonta bieleri sp. nov.

Figures 10 C, 13, 14H, 15F

Examined material (4 specimens). Holotype: MNHN 25209, Rr8. Paratypes: MNHN 25210, 1 shell, Rr35; MNHN 25211, 2 shells, Rr66.

Diagnosis: Shell with rounded periphery, coarse primary axial sculpture and prominent apertural barriers (four barriers and three traces on palatal wall; five barriers on parietal); umbilicus very narrow (width less than one tenth of the diameter of the shell).

Description: Shell depressed, white, with dark reddish-brown, scattered flammulations on the apical surface and shell base. Shell thin, opaque; periostracum adherent, matt. Apex barely raised, spire elevated, later whorls descending more rapidly. Apical and umbilical sutures impressed; whorls and periphery rounded. Transition between protoconch and teleoconch indistinct. Protoconch sculptured by very fine spiral and axial lirae, forming a reticulated pattern; spiral lirae fading on the transitional zone between protoconch and teleoconch. Axial lirae progressively transitioning into coarse ribs, with interspaces two to four times their width, comprising the primary sculpture of the teleoconch. Secondary sculpture of the teleoconch formed by crowded, wavy axial riblets, with interspaces approximately equal to their width, overlaying the primary sculpture. Umbilicus very narrow, deep. Peristome crescent-shaped; columellar lip reflected towards the shell axis, constricting the umbilicus in part. Palatal wall with four barriers and three traces, all recessed, extending approximately one-eighth whorl, with gradual anterior and posterior descension; all traces deeply recessed; first trace columellar in position, second and third traces infraperipheral and peripheral in position; barriers regularly spaced, similar in prominence, progressively transitioning from very shallowly recessed (first) to deeply recessed (fourth barrier); first barrier positioned at the confluence of basal and columellar lips; second and third barriers mid-basal in position; fourth barrier positioned at the confluence of basal and peripheral walls, as deeply recessed as traces. Parietal barriers five in number, not recessed within aperture, extending approximately one-quarter whorl, regularly spaced, with gradual anterior and somewhat abrupt posterior descension; barriers one to four similar in morphology; fifth barrier lower than the remainder. Other shell features that can be expressed numerically are shown in Table 2 .

Remarks: In overall shape, sculpture and coloration this species closely resembles M. boucheti , from which it is easily distinguished by its very narrow umbilicus. A relatively higher shell and a larger number of apertural barriers in M. bieleri appear to provide the most useful additional criteria for separation of these seemingly closely related species. For a comparison with Minidonta from Raivavae, refer to remarks under M. boucheti .

Etymology: The species is dedicated to Rüdiger Bieler, distinguished malacologist.

Figures

FIGURE 10. Holotypes of: A. Australdonta teaae sp. nov.; B. Minidonta boucheti sp. nov.; C. M. bieleri sp. nov. Scale bars = 1 mm.