Athleta (Volutopupa) citharopsis

Merle, Didier, Pacaud, Jean-Michel, Métais, Grégoire, Bartolini, Annachiara, Lashari, Rafiq A., Brohi, Imdad A., Solangi, Sarfraz H., Marivaux, Laurent & Welcomme, Jean-Loup, 2014, Volutidae (Mollusca: Gastropoda) of the Lakhra Formation (Earliest Eocene, Sindh, Pakistan): systematics, biostratigraphy and paleobiogeography, Zootaxa 3826 (1), pp. 101-138 : 119

Athleta (Volutopupa) citharopsis sp. nov.

( Fig. 8A–D )

Etymology. The two first syllables cithar because of the similarity with the type species, combined to the suffix opsis (Greek: appearance).

Type locality. Stn 4: Lakhra Dome, Lakhra village section, base of the Lakhra Formation.

Type material. Holotype (stn 4: CPAG.RAN. I.25, cast MNHN.F. A50363 ), paratype 1 (stn 4: CPAG.RAN. I.26, cast MNHN.F.A50364), paratype 2 (stn 4: CPAG.RAN. I.27, cast MNHN.F. A50365 ).

Other material. 3 spm (stn 4: MNHN).

Description. Shell of holotype large, H 60, D probably 31 mm (outer lip broken). Protoconch and first teleoconch whorl unknown; at least 6 teleoconch whorls. Spire moderately high, occupying 21% of total shell height. Spiral whorls convex; last whorl ventricose. Spiral sculpture of one row of very small subsutural nodules, appearing on third whorl. From fourth to fifth whorl, a second row of shoulder nodules ( Fig. 8D ) appears, becoming variably subspinose on penultimate whorl. On last whorl, spiral sculpture displaying: 1) adapically two main spiral rows of nodules (subsutural and shoulder rows); 2) no cords between these rows and mid-whorl; 3) from mid-whorl to base, ca. 15 flattened cords, producing an imbricate effect. Axial sculpture of collabral costae present on second whorl, extending across whorl, apparently without nodules. Third whorl: 15 costae; fourth whorl: 14 costae; fifth whorl: 13 costae; sixth whorl: 11 costae. On last (sixth) whorl, costae obsolete between adapical rows of nodules, thin and sharp below shoulder angle, extending across base, becoming almost obsolete towards end of last whorl; one intercostal ridge appearing at end of last whorl. Aperture ovate, occupying 78% of total height. Inner lip almost straight, columella with 3 to 4 low folds; inner lip callus very wide, parietal callus relatively thick, spreading far laterally, but not extending up to suture. Outer lip broken. Siphonal notch not well preserved, apparently weak.

Comparisons. This species differs from Athleta (Volutopupa) intercrenatus by its more ventricose shape, by its less numerous columellar folds and by its smaller subsutural and shoulder nodules. In shape and in its wide parietal callus, it resembles A. (V.) citharoedus , the type species of the subgenus. However, A. (V.) citharopsis can be easily distinguished from A. (V.) citharoedus by its stronger columellar folds and more strongly developed subsutural nodules.

Stratigraphic range. Lakhra Formation: Lakhra Dome.

Figures

FIGURE 8. A – D. Athleta (Volutopupa) citharopsis sp. nov., A – B (holotype, CPAG. RAN. I. 25, ventral (A) and dorsal (B) views, stn 4), C (paratype 1, CPAG. RAN. I. 26, dorsal view, stn 4), D (paratype 2, CPAG. RAN. I. 27, enlarged view of the spire, stn 4); E – J. Athleta (Volutocorbis) eugeniae Vredenburg, 1923, E – F (CPAG. RAN. I. 29, dorsal view (E) and enlarged view of the spire (F), stn 4), G – H (CPAG. RAN. I. 28, dorsal (G) and ventral (H) views, stn 4), I – J (CPAG. RAN. I. 30, dorsal (I) and ventral (J) views, stn 4). Scale bars: A – E, G – J = 10 mm; F = 5 mm.