Volutilithes sindhiensis

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 : 127

Volutilithes sindhiensis sp. nov.

( Fig. 11A–E )

Etymology. From Sindh, Pakistan province.

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

Type material. Holotype (stn 4: CPAG.RAN. I.42, cast MNHN.F.A50380), paratype 1 (stn 4: CPAG.RAN. I.43, cast MNHN.F. A50381 ), paratype 2 (stn 4: CPAG.RAN. I.44, cast MNHN.F.A50382).

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

Description. Shell biconic, H ca. 36, D 19 mm (holotype, H not complete 30.6, D 18.8 mm. Protoconch not preserved. Teleoconch of 5.5 whorls. Spire moderately high, occupying 20% of total shell height. Spire whorls shouldered, carinate. Last whorl conic. Suture linear, undulating between bases of costae. Axial sculpture of strong costae, not corresponding from whorl to whorl. Costae rather orthocline, extending from suture to suture on spire, spiny on the shoulder, extending to base on last whorl. First whorl: sculpture not preserved; second whorl: 12 costae; third whorl: 10 costae; fourth whorl: 11 costae; fifth and last whorls: 10–11 costae. No spiral sculpture. Aperture lenticular, angulate posteriorly, occupying 62% of total height, 35% of diameter. No posterior notch. Outer lip of aperture slightly thickened externally. Inner lip almost straight anteriorly, sinuous posteriorly. Parietal callus poorly developed, not spreading posteriorly. Three oblique columellar folds observed, but probably more present in complete specimens. Base of siphonal canal not preserved.

Comparisons. This third species of Volutilithes from the Lakhra Formation shares similarities in its dimensions with V. welcommei , but it is easily distinguishable by its spiny costae. A young specimen shows that spines on the costae appear very early in ontogeny (second whorl). In comparison, the costae of V. welcommei become angulate only over the two last whorls. The biconic shape and the spiny costae suggest resemblances to species of A. ( Volutospina ), but most species of A. ( Volutospina ) exhibit several rows of nodules on their early teleoconch whorls (subsutural and shoulder rows and two abapical rows), which are missing in V. welcommei .

Stratigraphic range. Lakhra Formation: Lakhra Dome.

Figures

FIGURE 11. A – E. Volutilithes sindhiensis sp. nov., A – B (holotype, CPAG. RAN. I. 42, dorsal (A) and ventral (B) views, stn 4), C – D (paratype 1, CPAG. RAN. I. 43, ventral (C) and dorsal (D) views, stn 4), E (paratype 2, CPAG. RAN. I. 44, juvenile, ventral view, stn 4); F – I. Pseudaulicina coxi sp. nov., F – G (holotype, CPAG. RAN. I. 45, ventral (F) and dorsal (G) views, stn 4), H (paratype 2, CPAG. RAN. I. 47, juvenile, dorsal view, stn 4), I (paratype 1, CPAG. RAN. I. 46, ventral view, stn 4). Scale bars: A – D, F – G, I = 10 mm; E, H = 5 mm.