Mautodontha (Garrettoconcha) occidentalis Sartori, Gargominy & Fontaine, 2014, sp. nov.
Creators: name: Sartori, André F.
name: Gargominy, Olivier
name: Fontaine, Benoît
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Stylommatophora
Endodontidae
Mautodontha
Mautodontha occidentalis

description: Mautodontha (Garrettoconcha) occidentalis sp. nov.
Figures 10 B; 12; 35D; 37B; 39.
Examined material (32 specimens). Holotype: MNHN 25573, Mk13. Paratypes: MNHN 25574, 8 shells, Mk13. Additional material: 13 shells, Mk13; 2 shells, Mk11; 1 shell, Mk12; 1 shell, Mk15; 6 shells, Mk16.
Type locality. West coast of Makatea, approximately 3 km south of Temao (15.85189°S; 148.28018°W). Cave. Limestone, alt. 10 m; station Mk13.
Diagnosis. Shell less than 3 mm in diameter, subdepressed, without flammulations; teleoconch sculptured by narrow, low and relatively crowded primary axial ribs (> 110 ribs on body whorl); umbilicus U-shaped; palatal wall with 5 barriers, the first often trace-like; parietal wall with 3 barriers.
Description. Shell subdepressed, white to light fawn, without flammulations. Shell wall thin, usually opaque, seldom subpellucid; periostracum adherent, shiny. Apex and spire elevated to strongly elevated; later whorls descending more rapidly. Apical and umbilical sutures impressed; whorls sharply rounded apically, broadly rounded along periphery and shell base; junction of basal and columellar walls usually marked by a tighter curvature. Transition between protoconch and teleoconch poorly marked, at c. 1 ¼ whorl. Axial sculpture of the protoconch composed of pairs of fine riblets separated by interspaces 10–15 times the width of an individual riblet; riblets within each pair separated by a narrow interspace 1–2 times their width. Spiral sculpture of the protoconch composed of approximately equidistant lirae with interspaces 6–8 times their width, fading out approximately at the end of the first whorl. Axial sculpture of the protoconch gradually transitioning into low ribs, with interspaces 4–6 times their width, which comprise the primary sculpture of the teleoconch. Secondary sculpture of the teleoconch composed of fine axial riblets occupying the interspaces between primary ribs; riblets initially wellspaced, 2–4 between each pair of ribs, crowded from the third whorl onwards, commonly with 8–10 riblets between each pair of primary ribs. Teleoconch devoid of spiral sculpture. Umbilicus very deep, U-shaped. Peristome crescent-shaped; columellar lip slightly reflected. Palatal wall with 5 barriers, all extending c. 1/8 whorl, descending somewhat abruptly anteriorly and posteriorly, regularly spaced and slightly recessed within the aperture; barrier 1 columellar in position, often trace-like and attaining only half the prominence of barrier 2; barriers 2 and 3 basal, 4 infraperipheral and 5 peripheral in position; barrier 5 slightly more deeply recessed and less prominent than barrier 4. Parietal barriers 3, extending c. 3/16 whorl, descending gradually anteriorly and abruptly posteriorly, similar in prominence, more or less regularly spaced, not recessed within the aperture. Other shell features that can be expressed numerically are shown in Table 2.
Remarks. M. (G.) occidentalis is the smallest endodontid recorded from Makatea (Fig. 35); although the examined specimens of M. (G.) temaoensis sp. nov. are only slightly larger, most display fewer than 5 whorls and are quite possibly subadults. M. (G.) occidentalis is somewhat variable in spire elevation and specimens with a lower spire approach the general shell shape of M. (G.) aurora; a higher peristome, less broadly rounded transition between basal and columellar walls, and slightly more crowded sculpture in M. (G.) occidentalis are, in addition to the smaller shell size, criteria for distinguishing these species.
Etymology. From occidentalis (Latin), alluding to the distribution of this species, which is only known from the western side of Makatea.
description: Published as part of Sartori, André F., Gargominy, Olivier & Fontaine, Benoît, 2014, Radiation and decline of endodontid land snails in Makatea, French Polynesia, pp. 1-68 in Zootaxa 3772 (1) on pages 20-21, DOI: 10.11646/zootaxa.3772.1.1, http://zenodo.org/record/285653