Mautodontha (Mautodontha) virginiae, 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 : 14-16

Mautodontha (Mautodontha) virginiae sp. nov.

Figures 6 B; 8; 35C; 37B; 39.

Examined material (167 specimens). Holotype: MNHN 25681, Mk19. Paratypes: MNHN 25682, 8 shells, Mk19. Additional material: 156 shells, Mk19; MNHN 25686, 1 shell, Mk18; 1 shell, Mk18.

Type locality. Coastal cliff north of Moumu, Makatea (15.81782°S; 148.25673°W). Accumulation zone in rocky substratum. Limestone, alt. 10 m; station Mk19.

Diagnosis. Shell less than 4 mm in diameter, depressed, flammulated; teleoconch sculptured by broad, relatively well-spaced primary axial ribs (<110 ribs on body whorl); umbilicus V-shaped; palatal wall with 5 barriers, the first often trace-like; parietal wall with 3 barriers, rarely accompanied by 2 traces.

Description. Shell depressed, white to fawn, with regularly spaced, amber flammulations persisting on shell base or fading out in the vicinity of the umbilical margin. Shell wall thin, opaque to pellucid; periostracum adherent, shiny. Apex barely raised, spire elevated; later whorls descending more rapidly. Apical and umbilical sutures impressed; whorls slightly flattened above rounded periphery; obtusely angled at the junction of basal and columellar walls. Transition between protoconch and teleoconch indistinct. Protoconch sculptured by fine axial riblets, initially with interspaces 8–12 times their width, becoming progressively crowded, transitioning into the secondary sculpture of the teleoconch. Spiral sculpture of the protoconch composed of lirae with interspaces 3–6 times their width, persisting on the surface of the teleoconch, forming tiny nodules at intersections with the secondary axial sculpture. Primary axial sculpture of the teleoconch composed of broad, prominent ribs, with interspaces c. 3–4 times their width, overlaid by a secondary axial sculpture of fine, crowded, wavy riblets, with interspaces c. 2–3 times their width. Umbilicus deep, V-shaped. Peristome crescent-shaped; columellar lip very slightly reflected. Palatal wall with 5 barriers, all extending c. 1/8 whorl, descending gradually anteriorly and posteriorly, approximately equidistant, recessed within the aperture; barrier 1 columellar in position, often tracelike; barriers 2 to 5 basal; barriers 3 and 4 slightly more prominent and less recessed than the others. Parietal wall with 3 barriers and, rarely, 2 traces; all parietal barriers extending c. 3/16 whorl, descending gradually anteriorly and posteriorly, not recessed within the aperture, approximately equidistant, similar in prominence. Trace 1 positioned between barriers 1 and 2; trace 2 between barriers 2 and 3. Other shell features that can be expressed numerically are shown in Table 2 .

Remarks. One of the specimens recovered from station Mk18 has the whorls much flattened below the periphery and four parietal barriers ( Fig. 8 E). Although it appears distinct from typical M. (M.) virginiae , ultrastructural examination failed to reveal any differences in the protoconch or teleoconch sculpture. Hence, in the absence of additional individuals displaying such morphology, we see this specimen as an aberrant M. (M.) virginiae . Additional field efforts at and around Mk18 are needed to re-evaluate this hypothesis.

In body size, coloration and shell shape, M. (M.) virginiae somewhat resembles M. (M.) daedalea , from which it is easily distinguished by its coarser and less dense primary ornamentation ( Table 2 ), higher spire and a more abrupt transition between the columellar and basal margins of the aperture. The relatively coarse ornamentation of M. (M.) virginiae also aids its distinction from M. (M.) harperae sp. nov., which has a similar general shape and body size but bears much finer sculpture and more prominent aperture barriers; in addition, M. (M.) harperae is not known to display flammulations. A wider umbilicus provides the easiest criterion for separating M. (M.) virginiae from the seemingly further related Mautodontha (Garrettoconcha) aurora sp. nov. and Kleokyphus cowiei sp. nov.

Etymology. This species is dedicated to our colleague Virginie Héros, of the Muséum national d’Histoire naturelle, for her continuous support.

Figures

FIGURE 6. Holotypes of: A. Mautodontha (Mautodontha) domaneschii sp. nov.; B. Mautodontha (Mautodontha) virginiae sp. nov.; C. Mautodontha (Mautodontha) harperae sp. nov. Scale bars = 2 mm.

FIGURE 8. Mautodontha (Mautodontha) virginiae sp. nov. A – C. Holotype (MNHN 25681), apical views; A. General view; B. Sculpture of the protoconch and early teleoconch; C. Sculpture of the late teleoconch; D. Paratype 1 (MNHN 25682), detail of the peristome; E. Aberrant specimen (MNHN 25686) from station Mk 18; Scale bars: A = 1 mm; B – C = 0.2 mm; D = 0.4 mm; E = 2 mm.