Pseudaulicina coxi

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 : 127-128

Pseudaulicina coxi sp. nov.

( Fig. 11 F–I)

Etymology. Dedicated to L. R. Cox for his work on the Hangu Formation.

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

Type material. Holotype (stn 4: CPAG.RAN. I.45, cast MNHN.F. A50383 ), paratype 1 (stn 4: CPAG.RAN. I.46, cast MNHN.F.A50384), paratype 2 (stn 4: CPAG.RAN. I.47, cast MNHN.F. A50385 ).

Other material. 5 spm (stn 4: MNHN).

Description. Shell biconic, H probably 60 mm, to judge from largest fragment (holotype H 32.8 not complete, D 20.7 mm). Largest and most complete specimen: H 40, D 22 mm. Protoconch not preserved. Teleoconch of probably 6–7 whorls. Spire relatively high, occupying 32% of total shell height. Spire whorls shouldered, with low carina formed by shoulder spines. Last whorl moderately wide, excavated at beginning of siphonal canal. Suture linear, with weak undulation between bases of costae. Axial sculpture of strong but rounded costae. Costae slightly orthocline, subvertical on early whorls, with acute shoulder spines increasing in prominence until last whorl. On last whorl, costae obsolete from suture to shoulder spine, thick and relatively high below shoulder angle, extending across base, becoming almost obsolete towards end of last whorl. First whorl: not preserved; second and third whorls: 10 costae; fourth and fifth whorls: 9–10 costae; sixth whorl: not preserved. No apparent spiral sculpture. Aperture narrow, acutely angular posteriorly, occupying 55% of total height, 30% of diameter. No posterior notch. Outer lip slightly thickened externally. Inner lip sinuous posteriorly (base not preserved). Parietal callus thin, not spreading posteriorly. Four strong, oblique columellar folds, anterior-most weaker. Siphonal canal not preserved.

Comparisons. Because of its proportions, its axial sculpture on the early teleoconch whorls and the aspect of its columella, this species is very close to Pseudaulicina vredenburgi ( Cox, 1930) from the Hangu Formation. The specimens described by Cox (1930) do not exceed 40 mm in height, like most of the complete specimens collected in the Lakhra Dome, which are probably juveniles. Cox (1930: 197) stated that the spiral sculpture of P. vredenburgi consists of numerous closely and rather irregularly spaced striae, covering the whole surface, and extending anteriorly well down the stem of the shell. This sculpture is missing in the specimens of P. coxi , which have a smooth surface. According to Cox (1930), P. vredenburgi can be compared to P. mitrata (Deshayes, 1835) from the Lutetian of the Paris Basin and to P. wateleti (Deshayes, 1865) from the Ypresian of the Paris and Aquitaine basins. P. mitrata is probably a variant of the type species of Pseudaulicina, P. musicalis ( Lamarck, 1803) , bearing a more elongate spire and stronger spiral cords than the more common specimens. P. musicalis differs from P. vredenburgi and P. coxi by having spiral cords and by its angulate shoulder spines. In addition, large specimens of P. musicalis display one or two posterior folds, which are missing in the two Pakistani species. P. wateleti shares with P. vredenburgi and P. coxi acute shoulder spines and four strong columellar folds. The surface of P. wateleti seems smooth as in P. coxi , but a careful examination of the last whorl of several specimens revealed low spiral cords as in P. musicalis . Although these cords are obsolete, they differ from the fine threads of P. vredenburgi .

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.