Volutilithes welcommei

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 : 126-127

Volutilithes welcommei sp. nov.

( Fig. 10 E–H)

Etymology. Dedicated to Jean-Lou Welcomme.

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

Type material. Holotype (stn 4: CPAG.RAN. I.39, cast MNHN.F. A50377 ), paratype 1 (stn 4: CPAG.RAN. I.40, cast MNHN.F.A50378), paratype 2 (stn 4: CPAG.RAN. I.41, cast MNHN.F. A50379 ).

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

Description. Shell biconic, H 38–39, D 19–20 mm (holotype H 38.5, D 20.1 mm. Protoconch smooth, rounded, bulbous, of 1¾ whorls ( Fig. 10 F). Transition protoconch/teleoconch not defined. Teleoconch of 5 whorls. Spire moderately high, occupying 24% of total shell height. Two first whorls spire whorls convex, later whorls subcarinate. Last whorl narrow, rather conic. Suture linear, undulating between bases of costae. Axial sculpture of strong but narrow, rounded costae, not corresponding from whorl to whorl. Costae slightly orthocline, extending from suture to suture on spire, angulate at shoulder, extending to base of last whorl. First whorl: 12 costae; second whorl: 10–11 costae; third whorl: 9–10 costae; fourth whorl: 10–11 costae; fifth and last whorls: 9–12 costae. No spiral sculpture on spire. Spiral sculpture of fine threads on base of last whorl. Aperture lenticular, occupying 67% of total height, 29% of diameter. No posterior notch. Outer lip slightly thickened externally. Inner lip almost straight anteriorly, sinuous posteriorly. Parietal callus slightly developed, spreading posteriorly. Five oblique columellar folds, the most posterior being weaker. Siphonal canal short, slightly curved dorsally; siphonal fasciole low, weak; siphonal notch very shallow.

Comparisons. From the Lakhra Formation, this species can be compared to Volutilithes jhirakensis Vredenburg, 1923 [ V. jhirakensis Cossmann & Pissarro, 1909 is a nomen nudum]. V. welcommei is distinguished from V. j h i r a ke n s i s by its wider shape and lower spire. The costae of V. jhirakensis are elongate, whereas they are angulate in V. welcommei . By its elongate shape, V. jhirakensis recalls the Lutetian species from the Paris Basin, V. torulosus (Deshayes, 1835) , whereas the low-spired shape and the angulate costae of V. welcommei are more similar to those of V. torreyensis Givens, 1978 from the early Middle Eocene of California.

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.