Lyrischapa blanfordi ( Vredenburg, 1923 )

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 : 114-116

Lyrischapa blanfordi ( Vredenburg, 1923) comb. nov.

( Fig. 6A–F )

Athleta blanfordi Vredenburg, 1923: 255 .

Aulicina haimei (non Voluta haimei d’Archiac & Haime, 1853 ). Cossmann & Pissarro 1909: 25, pl. 2, fig. 27 only.

Athleta blanfordi . Cotter in Vredenburg 1928: 36.

Description. Shell biconic, elongate, H 68–85, D 30–50 mm. Protoconch smooth, globose and slightly deviated, of two whorls, H 6, D 10 mm when complete. Protoconch/teleoconch transition not obvious. Teleoconch of 3 whorls. Spire low, occupying 6% of total shell height. Spire whorls almost flat, separated by shallow suture undulating between shoulder spines of preceding whorl. Last whorl elongate, rather conical. Spiral sculpture on spire of obsolete threads, visible only on first teleoconch whorl. On juvenile specimens of one whorl, last whorl sculptured by very fine threads, covering abapical three quarters of shell, disappearing on succeeding whorls. Axial sculpture of only spiny shoulder costae. Shoulder spines oriented adapically on last whorl. First whorl: 11 costae, becoming more prominent on second half of whorl. Second whorl: 8–9 costae; third whorl: 8–9 costae. No anal sulcus. Aperture narrow, occupying 89% of total height, 18% of diameter. Inner lip straight, columella with six strong folds succeeded posteriorly by two weaker folds; inner lip callus narrow. Outer lip thin, not thickened externally. Siphonal canal short, slightly curved to right towards aperture; siphonal notch weak; siphonal fasciole low, weak, but delineated by carina spreading dorsally on gerontic specimens.

Material. 28 spm (stn 4: 3 spm CPAG.RAN. I.15–17, cast MNHN.F. A50353 –55 and 25 spm MNHN).

Comments. Although Cossmann & Pissarro (1909) confounded specimens of L. haimei with L. blanfordi , L. blanfordi was originally described in the genus Athleta and later Givens (1991) did not discuss it in his revision of the genus Lyrischapa . Vredenburg (1923) compared L. blanfordi with two Bartonian species from the Anglo-Parisian Basin: Athleta (A.) athleta (Solander in Brander, 1766) and A. (A.) strombiformis (Deshayes, 1835) . These species exhibit a biconic shape and have shoulder spines, so generating a superficial resemblance with L. blanfordi , but they differ by their early teleoconch whorls and by their columellar folds. In A. (A.) athleta and A. (A.) strombiformis , the early teleoconch whorls have two main spiral rows of nodules (subsutural and shoulder rows) and one or two abapical rows. This kind of sculpture is typical of Paleogene Athleta (Athleta) species and it is present in other subgenera such as A. ( Volutospina ), A. (Volutopupa) an d A. ( Volutocorbis ). However, it is absent in Lyrischapa , which has only a single shoulder row during the ontogenetic development of the shell. A. (A.) athleta and A. (A.) strombiformis also bear three strong columellar folds and several weaker folds adapically, whereas in L. blanfordi the number of folds varies from 6 to 8. In L. blanfordi , as in other members of Lyrischapa , these folds are stronger in most specimens than those observed in the two Bartonian Athleta species and other Paleogene Athleta species. Therefore, it is with little uncertainty that we transfer L. blanfordi to the genus Lyrischapa .

Stratigraphic range. Lakhra Formation: Jhirak ( Vredenburg 1923), Lakhra Dome (this paper).

Figures

FIGURE 6. A – F. Lyrischapa blanfordi (Vredenburg, 1923), A – C (CPAG. RAN. I. 17, ventral (A), dorsal (B) and apical (C) views, stn 4), D – E (CPAG. RAN. I. 16, ventral (D) and dorsal (E) views, stn 4), F (CPAG. RAN. I. 15, ventral view, stn 4); G – I. Lyrischapa brevispira sp. nov., holotype, CPAG. RAN. I. 18, ventral (G), dorsal (H) and apical (I) views, stn 4. Scale bars: A – H = 10 mm.