Mautodontha (Garrettoconcha) passosi, 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 : 25-26

Mautodontha (Garrettoconcha) passosi sp. nov.

Figures 14 B; 16; 35G; 37E; 39.

Examined material (146 specimens). Holotype: MNHN 25578, Mk19. Paratypes: MNHN 25579, 8 shells, Mk19. Additional material: 136 shells, Mk19; 1 shell, Mk04.

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, subdepressed, without flammulations; teleoconch sculptured by narrow, tall, relatively crowded primary axial ribs (> 80 ribs on body whorl); umbilicus U-shaped; palatal wall with 4 low barriers; parietal wall with 2 barriers.

Description. Shell subdepressed, white, without flammulations. Shell wall thin, opaque; periostracum adherent, matt. Apex and spire strongly elevated; later whorls descending more rapidly. Apical and umbilical sutures impressed; whorls and periphery rounded; columellar wall somewhat flattened. Transition between protoconch and teleoconch indistinct. Axial sculpture of the protoconch initially composed of pairs of fine riblets separated by interspaces 10–15 times the width of an individual riblet; riblets within each pair initially separated by a narrow interspace 2–3 times their width, subsequently coming closer and progressively merging into narrow, tall ribs, which comprise the primary sculpture of the teleoconch. Single axial riblets between pairs occurring approximately from the second quarter 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 3–5 times their width, persisting on the surface of the teleoconch, forming tiny nodules at intersections with the secondary axial sculpture. Umbilicus very deep, U-shaped. Peristome crescentshaped; columellar lip slightly reflected. Palatal wall with 4 low barriers, all extending c. 1/8 whorl, descending gradually anteriorly and posteriorly, regularly spaced and slightly recessed within the aperture; barrier 1 columellar in position; barriers 2 to 4 basal. Parietal wall with 2 barriers, both extending c. 1/8 whorl, descending somewhat abruptly anteriorly and gradually posteriorly, similar in prominence, taller than palatal barriers, not recessed within the aperture. Other shell features that can be expressed numerically are shown in Table 2 .

Remarks. M. (G.) passosi is similar to M. (G.) makateaensis and M. (G.) spelunca sp. nov. in the presence of two parietal barriers, but differs from both in bearing four palatals. Also, it differs from M. (G.) makateaensis in exhibiting more closely-set sculpture and usually a slightly higher spire; and from M. (G.) spelunca in having a smaller shell at the same whorl count.

Etymology. This species is dedicated to Flávio Dias Passos, who introduced the first author to malacology.

Figures

FIGURE 14. Holotypes of: A. Mautodontha (Garrettoconcha) makateaensis sp. nov.; B. M. (G.) passosi sp. nov.; C. M. (G.) spelunca sp. nov. Scale bars = 2 mm.