Mastonia obesula Jousseaume, 1884

Albano, Paolo G., Franco, Davide Di, Azzarone, Michele, J., Piet A., Bakker & Sabelli, Bruno, 2023, Review of the types of Indo-Pacific Triphoridae (Mollusca, Gastropoda) in the Muséum national d’Histoire naturelle, Paris, Zoosystema 45 (2), pp. 13-106 : 86

Mastonia obesula Jousseaume, 1884

( Fig. 58 )

Mastonia obesula Jousseaume, 1884: 255 , pl. 4, fig. 17.

TYPE LOCALITY. — New Caledonia.

TYPE MATERIAL. — Lectotype. New Caledonia • MNHN-IM-2000-29265; from type locality, here designated.

Paralectotypes. Triphoridae indet. New Caledonia • MNHN-IM-2000-1614; 5 specimens.

ORIGINAL DESCRIPTION. — Testa ovata, solidula, ventricosa, apice attenuata; anfractibus 13, seriebus tuberculorum tribus ornatis (séries média minuta, altéras aequales), sutura vix dis- tincta separatis; ultimo ad basin luteo - tincto, costis quinque moniliformibus ornato; apertura piriformi, lateraliter fissa; canali brevi. — Long, 4, lat. 1,5 millim.

[Latin diagnosis followed by a discussion in French]

TRANSLATION OF THE LATIN TEXT. — Ovate shell, rather solid, broad, reduced apex; 13 whorls, adorned by three series of tubercles (the median series is smaller, other series are equal), separated by a barely distinct suture; the last whorl is coloured in yellow at the base and adorned by five tubercled spiral cords; pyriform aperture, laterally fissured; short siphon. — Length 4, diameter 1.5 mm.

DIAGNOSIS. — Shell cyrtoconoid. Lectotype 3.4 mm high.Teleoconch of 7.5 whorls. Three spiral cords present, the second appearing on the sixth whorl. First and third cords with tubercles at the intersection with rather prosocline axial ribs. Second cord initially as a fine thread, but later developing thin tubercles. Spiral microsculpture of barely visible fine threads. Peristome with additional cords below the second and third spiral cord. Posterior sinus relatively deep. Base with three additional spiral cords of which the first developing tubercles, the other two smooth. Protoconch incomplete in the syntype, but clearly multispiral with one spiral keel and equally strong axial riblets.Teleoconch and protoconch brown, with the first teleoconch whorl and the base lighter.

REMARKS. — Lot MNHN-IM-2000-1614 contained six specimens belonging to two, if not more, species. One morphotype ( Fig. 57 B-K) is more slender, uniformly brown except the yellowish base, bears two main tubercled spiral cords with a third developing as a thin thread until the last whorl where it is fully developed. The second morphotype ( Fig. 57I ) is broader and with a marbled colour pattern with irregularly positioned lighter tubercles and darker interspaces. Due to Jousseaume’s reference to the yellow base (“ ultimo ad basin luteo - tincto ”), we here consider that the first morphotype represents M. obesula and here designate its lectotype to stabilize the nomenclature.

Figures

FIG. 58. — Mastonia obesula Jousseaume, 1884, New Caledonia: A, original figure in Jousseaume (1884); B-H, J, K, M, lectotype, MNHN-IM-2000-29265: front (B, C), side (D, E), back (F), peristome (G, H), apex (J, K), microsculpture (M); I, Triphoridae indet., MNHN-IM-2000-1614; front; L, N, O, original labels. Scale bars: B-F, I, 0.5 mm; G, H, M, 0.2 mm; J, K, 0.1 mm.

FIG. 57. — Inella numerosa Jousseaume, 1898, Perim Island, Bab al-Mandab Strait,Yemen: A-J, lectotype, MNHN-IM-2000-29264: front (A, B), side (C, D), back (E), peristome (F, G), microsculpture (H), protoconch (I, J); K-U, Triphoridae indet. (non Inella numerosa), Perim Island, Bab al-Mandab Strait, Yemen, MNHN- IM-2000-509: protoconch (K, L), front (M, N), side (O, P), back (Q), first protoconch whorl (R), microsculpture (S), peristome (T-U); V, Triphoridae indet. (non Inella numerosa), Perim Island, Bab al-Mandab Strait, Yemen,paralectotype,MNHN-IM-2000-509: front; W, Triphoridae indet. (non Inella numerosa), Perim Island,Bab al-Mandab Strait,Yemen,paralectotype,MNHN-IM-2000-509: front;X, Triphoridae indet.(Inella numerosa?), Perim Island,Bab al-Mandab Strait,Yemen,paralectotype, MNHN-IM-2000-509: front; Y-Z, original labels lot MNHN-IM-2000-509. Scale bars: A-E, M-Q, V-X, 1 mm; F, G, T-U, 0.4 mm; H-L, S, 0.2 mm; R, 0.1 mm.