Lyrischapa vredenburgi

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 : 112-114

Lyrischapa vredenburgi sp. nov.

Fig. 5A–H

Aulicina haimei (non Voluta haimei d’Archiac & Haime, 1853 ). Cossmann & Pissarro 1909: 25, pl. 2, fig. 30, pl. 8, fig. 2. Athleta blanfordi Vredenburg, 1923 pars: 255, proposed for Aulicina haimei d’Archiac & Haime, 1853 sensu Cossmann & Pissarro, 1909 , pl. 8, fig. 2 only.

Lyrischapa sismondai (non Voluta haimei d’Archiac & Haime, 1853 ). Givens 1991, 666, figs 4.3, 4.6.

Etymology. Dedicated to E. W. Vredenburg for his work on the geology and paleontology of the Ranikot Group.

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

Type material. Holotype (stn 4: CPAG.RAN. I.11, cast MNHN.F. A50349 ), paratype 1 (stn 4: CPAG.RAN. I.12, cast MNHN.F.A50350), paratype 2 (stn 4: CPAG.RAN. I.13, cast MNHN.F. A50351 ), paratype 3 (stn 4: CPAG.RAN. I.14, cast MNHN.F.A50352), three paratypes (Jhirak, Cossmann coll. MNHN.F. J12751 ).

Other material. 16 spm (stn 4: MNHN); 3 spm (stn 5: MNHN).

Description. Shell biconical, wide, H 77–85, D 54–65 mm (holotype (subadult) H 38.3, D 31.1 mm). Protoconch smooth, globose, slightly deviated, of two whorls; H 16, D 11 mm when complete ( Fig. 5A–B ). Transition from protoconch to teleoconch not defined. Teleoconch of 3 to 3.5 whorls. Spire low, occupying 10% of total shell height. Spiral whorls almost flat, separated by shallow suture undulating between shoulder spines of preceding whorl. Last whorl rather triangular. Spiral sculpture on spire of obsolete threads, visible only on first teleoconch whorl. On juvenile specimens of one whorl, last whorl sculptured with very fine spiral threads covering three abapical quarters of shell, threads disappearing on succeeding whorls. Axial sculpture of spiny shoulder costae only. First whorl: 11 costae, becoming more prominent on second half of whorl. Second whorl: 9–10 costae; third whorl: 9–12 costae. No shoulder sinus. Aperture narrow, occupying 87% of total height, 28% of diameter. Inner lip straight, columella with five strong folds succeeded posteriorly by one weaker fold; inner lip callus narrow. Outer lip thin, not thickened externally. Siphonal canal short; siphonal notch weak; siphonal fasciole low, weak, but delineated by carina spreading dorsally on gerontic specimens.

Comparisons. From the Lakhra Formation, this species can be compared with Lyrischapa blanfordi ( Vredenburg, 1923) . Both species share obsolete threads on the first teleoconch whorl and the disappearance of the spiral sculpture on the last few whorls. As in L. vredenburgi , L. blanfordi exhibits shoulder spines and lacks a shoulder sinus. L. blanfordi differs in its less numerous costae on the last whorl (8–9 instead of 9–12), its shoulder spines oriented adapically and its narrower shape. The number of columellar folds varies from 5 to 6, whereas those of L. blanfordi vary from 6 to 8. L. vredenburgi also has a strong similarity to L. crassa ( Douvillé, 1929) described from the Danian of the Kadhro Formation, at Jakhmari and at Ranikot. The two species share a wide biconic shape, a low spire, 12 costae on the last whorl and the presence of shoulder spines. The type specimen of L. crassa is poorly preserved, but it apparently differs from A. vredenburgi by having only four columellar folds and more rounded shoulder spines. L. crassa was originally assigned to Diconomorpha , but the close similarities between A. crassa and A. vredenburgi constitute a further argument to consider Diconomorpha as a junior synonym of Lyrischapa .

Stratigraphic range. Lakhra Formation at Lakhra and Jhirak; Nammal Formation, Salt Range ( Givens 1991).

Figures

FIGURE 5. A – H. Lyrischapa vredenburgi sp. nov., A – B (paratype 1, CPAG. RAN. I. 12, protoconch and first teleoconch whorl in ventral (A) and dorsal (B) views, stn 4), C – E (holotype, CPAG. RAN. I. 11, ventral (C), dorsal (D) and apical (E) views, stn 4), F (paratype 2, CPAG. RAN. I. 13, ventral view, stn 4), G (paratype 3, CPAG. RAN. I. 14, ventral view, stn 4), H (paratype MNHN. F. J 12751, Cossmann coll., Jhirak). Scale bars: A – H = 10 mm.