Minidonta boucheti, 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

Minidonta boucheti sp. nov.

Figures 10 B, 12, 14G, 15B

Examined material (48 specimens). Holotype: MNHN 25207, Rr68. Paratypes: MNHN 25208, 8 shells, Rr68. Additional material: 11 shells, Rr68; 3 shells, Rr4; 13 shells, Rr8; 1 shell, Rr20; 1 shell, Rr30; 1 shell, Rr35; 3 shells, Rr42; 1 shell, Rr45; 4 shells, Rr57; 1 shell, Rr66.

Diagnosis: Shell with rounded periphery, coarse primary axial sculpture and prominent apertural barriers (five palatal barriers, rarely accompanied by one or two traces; four to six parietal barriers); umbilicus wider than one sixth of the diameter of the shell.

Description: Shell depressed, white, with or rarely without light to dark reddish-brown flammulations on the apical surface of the shell; flammulations usually fading out towards the shell base, less commonly persisting and transitioning to scattered, oblique markings. Shell thin, usually opaque, rarely subpellucid; periostracum adherent, matt. Apex flat to barely elevated, spire slightly to moderately raised, last whorl descending more rapidly. Apical and umbilical sutures impressed; whorls and periphery evenly 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 three to four times their width, comprising the primary sculpture of the teleoconch. Secondary sculpture of the teleoconch formed by crowded axial riblets, with interspaces approximately equal to their width, overlaying the primary sculpture. Umbilicus wide, deep. Peristome crescent-shaped. Palatal wall with five prominent barriers and, rarely, one or two additional traces; barriers shallowly recessed, extending approximately one-eighth whorl, approximately regularly spaced, with gradual anterior and somewhat abrupt posterior descension; first to fourth barriers basal in position, similar in prominence; fifth barrier supraperipheral, slightly narrower and less prominent than the remainder. First palatal trace columellar in position, slightly more deeply recessed than barriers; second trace peripheral, positioned equidistantly between fourth and fifth barriers, slightly more deeply recessed than first trace, very low. Parietal barriers usually four, less commonly five or rarely six in number, with gradual anterior and abrupt posterior descension, gradually decreasing in prominence from the first to the fourth barrier; fifth and sixth barriers markedly less prominent than remainder. Barriers one to five not recessed within aperture; barrier six slightly recessed. Other shell features that can be expressed numerically are shown in Table 2 .

Remarks: Minidonta boucheti is sympatric with and resembles M. haplaenopla Solem, 1976 in size and shape, but is distinguished from that species by its coarser, more prominent primary axial sculpture, and by its larger number of apertural barriers. Diameter of the umbilicus provides the easiest and most reliable basis for separating M. boucheti and M. bieleri sp. nov. —it is wide in the former and very narrow in the latter species. Within the Austral Islands, species of Minidonta Solem, 1976 have been previously recorded only from Rurutu ( M. haplaenopla ) and Raivavae (five species). All display much narrower axial ribs than M. boucheti and M. bieleri , being hence readily distinguished. In addition, the five species from Raivavae may be separated from M. boucheti and M. bieleri using the following criteria: M. micraconica Solem, 1976 and M. gravacosta Solem, 1976 are much smaller and display a bifid first parietal barrier; M. anatonuana Solem, 1976 has narrower axial ribs, a higher apex and an umbilicus that is narrower than in M. boucheti but much wider than in M. bieleri ; M. sulcata Solem, 1976 exhibits more crowded axial sculpture, reduced number of apertural barriers and wider umbilicus; and M. planulata Solem, 1976 is larger, more depressed and has a more rounded aperture.

Etymology: The species is dedicated to Philippe Bouchet, who introduced OG and BF to malacology and invited AS to participate in this work.

Figures

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