Athleta (Volutocorbis) lasharii

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 : 124

Athleta (Volutocorbis) lasharii sp. nov.

( Fig. 10A–D )

Etymology. Dedicated to Doctor Rafique Ahmed Lashari, Centre for Pure and Applied Geology, University of Sindh, Jamshoro, Pakistan.

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

Type material. Holotype (stn 4: CPAG.RAN. I.37, cast MNHN.F. A50375 ), one paratype (stn 4: CPAG.RAN. I.38, cast MNHN.F.A50376).

Other material. 2 spm (stn 4: MNHN).

Description. Shell biconic, slightly fusiform, H 40–48, D ca. 20–22 mm (holotype H 43.5, D 19.6 mm, outer lip not complete. Protoconch and two first teleoconch whorls unknown; at least 5 teleoconch whorls. Spire moderately high, occupying 20% of total shell height. Spire whorls weakly convex, last whorl rather oval. Spiral sculpture on spire of a first row of rounded subsutural nodules, appearing on third whorl and becoming more developed aperturally; abapically, three rows of rounded nodules including shoulder row, which is less distinct than others ( Fig. 10C ). On last whorl, spiral sculpture displaying: 1) subsutural row of spiny nodules; 2) shoulder row of spiny nodules; 3) between shoulder and mid-whorl, 9 to 10 rows of almost flat cords, separated by narrow spiral grooves; 4) from mid-whorl to base, nodules and cords produce imbricate effect. From second to penultimate whorl, costae interrupted by rows of nodules. On last whorl, costae obsolete between subsutural and shoulder nodules, narrow but relatively high below shoulder angle, extending across base, becoming almost obsolete towards end of last whorl. Second whorl: 12 costae; third whorl: 14 costae; fourth whorl: 12–14 costae; fifth and last whorl: 9–13 costae. Aperture ovate, rather narrow, occupying 72% of total height, 61% of diameter. Inner lip straight, columella with one fold, succeeded posteriorly by several weaker and smaller folds; inner lip callus very narrow, spreading a little anteriorly. Outer lip thin, not thickened externally. Siphonal canal slightly elongate; siphonal notch shallow.

Comparisons. Athleta (Volutocorbis) lasharii sp. nov. differs from the other Sindh species of A. ( Volutocorbis ) in its larger size, its spiral sculpture on the last whorl characterized by the loss of crenulations or nodules between the shoulder and the mid-whorl and by its axial sculpture of higher, narrow costae. Such sculpture distinguishes it from the A. (V.) digitalinus- type species bearing strongly nodular sculpture on the last whorl (e.g. A. (V.) burtoni , A. (V.) daviesi and A. (V.) soriensis from the Early Paleogene of Pakistan) and the A. (V.) elevatus - type species bearing crenulate sculpture (e.g. A. (V.) eugeniae and A. (V.) wynnei from the Early Paleogene of Pakistan). The type of sculpture displayed in A. (V.) lasharii sp. nov. more resembles that of A. (V.) bicorona ( Lamarck, 1803) from the Lutetian of the Paris Basin. A. (V.) bicorona shares a last whorl characterized by the loss of crenulations or nodules between the shoulder and the mid-whorl. Moreover, both species have two rows of spiny nodules developed adapically (the subsutural and shoulder rows). A (V.) bicorona differs, however, from A. (V.) lasharii sp. nov. by its early whorls having two more abapical spiral rows of crenulations. In A. (V.) bicorona , a residual color pattern observed under UV light has been reported ( Merle et al. 2008), but the recrystallized shells of A. (V.) lasharii did not reveal any traces of a residual color pattern.

Stratigraphic range. Lakhra Formation: Lakhra Dome.

Figures

FIGURE 10. A – D. Athleta (Volutocorbis) lasharii sp. nov., A – C (holotype, CPAG. RAN. I. 37, dorsal (A) and ventral (B) views, enlarged view of the spire (C), stn 4), D (paratype, CPAG. RAN. I. 38, dorsal view, stn 4); E – H. Volutilithes welcommei sp. nov., E (paratype 1, CPAG. RAN. I. 40, dorsal view, stn 4), F (paratype 2, CPAG. RAN. I. 41, juvenile, dorsal view, stn 4), G – H (holotype, CPAG. RAN. I. 39, ventral (G) and (H) dorsal views. Scale bars: A – B, D – E, G – H = 10 mm; C, F = 5 mm.