Mautodontha (Garrettoconcha) aurora, 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 : 17-19

Mautodontha (Garrettoconcha) aurora sp. nov.

Figures 10 A; 11; 35F; 38B; 39.

Examined material (234 specimens). Holotype: MNHN 25575, Mk22. Paratypes: MNHN 25576, 2 shells, Mk22; MNHN 25577, 6 shells, Mk04. Additional material: 201 shells, Mk04; 18 shell, Mk19; 6 shells, Mk20.

Type locality. Plateau west of Anapoto, Makatea (15.83987°S; 148.22852°W). Karst (feo) on top of cliff with Ficus sp. and Pandanus sp. Limestone, alt. 75 m; station Mk22.

Diagnosis. Shell less than 3.5 mm in diameter, depressed, without flammulations; teleoconch sculptured by narrow, tall and relatively crowded primary axial ribs (> 110 ribs on body whorl); umbilicus U-shaped; palatal wall with 5 barriers; parietal wall with 3 barriers.

Description. Shell depressed, white to fawn, without flammulations. Shell wall thin, opaque to subpellucid; periostracum adherent, shiny. Apex and spire elevated; later whorls descending more rapidly. Apical and umbilical sutures impressed; whorls and periphery rounded; basal and columellar walls transitioning smoothly. Transition between protoconch and teleoconch indistinct. Axial sculpture of the protoconch initially composed of pairs of fine riblets separated by interspaces 8–12 times the width of an individual riblet; riblets within each pair initially separated by an interspace 3–4 times their width, subsequently coming closer and progressively merging into prominent ribs, which comprise the primary sculpture of the teleoconch. Single axial riblets between pairs occurring approximately from the second half of the first whorl, progressively increasing in number and transitioning into the secondary sculpture of the teleoconch. 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. Teleoconch sculptured by narrow, tall, prominent axial ribs, with interspaces 3–4 times their width, overlaid by a secondary ornament of crowded axial riblets, with interspaces approximately equal to their width. Teleoconch devoid of spiral sculpture. Umbilicus deep, U-shaped. Peristome crescent-shaped; columellar lip very slightly reflected. Palatal wall with 5 barriers, all extending c. 1/8 whorl, descending gradually anteriorly and somewhat abruptly posteriorly, regularly spaced and slightly recessed within the aperture; barrier 1 columellar, 2 and 3 basal, 4 infraperipheral and 5 peripheral in position; barrier 5 slightly more deeply recessed and usually less prominent than barrier 4. Parietal barriers 3, extending c. 3/16 whorl, descending gradually anteriorly and abruptly posteriorly, similar in prominence, regularly spaced, not recessed within the aperture. Other shell features that can be expressed numerically are shown in Table 2 .

Remarks. A much larger shell at the same whorl count in M. (G.) aurora provides the best criterion for distinguishing this species from M. (G.) occidentalis sp. nov.; other differences include slightly less crowded sculpture, smoother transition between basal and columellar walls, lower peristome, and usually a less elevated spire in M. (G.) aurora . In general shell shape, M. (G.) aurora resembles M. (M.) virginiae and M. (M.) harperae , but it is easily distinguished from those species by its narrower, U-shaped umbilicus.

Etymology. From aurora (Latin) , meaning sunrise, alluding to the distribution of this species, which is only known from the eastern side of Makatea. Aurora is also a former European name for Makatea.

Figures

FIGURE 10. Holotypes of: A. Mautodontha (Garrettoconcha) aurora sp. nov.; B. M. (G.) occidentalis sp. nov.; C. M. (G.) temaoensis sp. nov. Scale bars = 2 mm.