Plagiostoma? sp. B

Fuersich, Franz T., Alberti, Matthias, Pandey, Dhirendra K. & Ayoub-Hannaa, Wagih S., 2022, Jurassic bivalves from the Spiti area of the Himalayas, northern India, Zitteliana 96, pp. 153-178 : 153

Plagiostoma? sp. B

Plate 4, fig. 6

Material.

A fragmented left internal mould with remains of the inner shell layer from the Ferruginous Oolite Formation near Zangla (SNSB-BSPG 2020 XCIX 36).

Description and remarks.

As the ventral part of the specimen is missing, its outline remains unknown, but most likely was obliquely triangular-ovate. The hinge line is short and straight, the umbo orthogyrate, the posterior auricle distinctly set off from the flank. The shell surface is ornamented with indistinct remnants of radial ribs. It differs from Plagiostoma ? sp. A in outline and style of ribbing. The few features that can be observed all support the placement of the specimen in Plagiostoma or a related genus.

Figures

Plate 4. (1) Camptonectes (Camptochlamys) sp. from the upper member close to Demul Pass (SNSB-BSPG 2020 XCIX 14). (2) Chlamys (Chlamys) cf. textoria (Schlotheim, 1820). Incomplete right valve from the lower member at Langza (SNSB-BSPG 2020 XCIX 11). (3) Spondylopecten (Plesiopecten) subspinosus (Schlotheim, 1820). Internal mould of right valve from the lower member at the Kaza-Hikkim road (SNSB-BSPG 2020 XCIX 23). (4) Radulopecten cf. fibrosus (J. Sowerby, 1816). a, b, Fragment of a right valve from the? lower member near Demul (SNSB-BSPG 2020 XCIX 39). (5) Pectinidae indet. Slightly distorted internal mould of a single valve from the lower member along the Kazan-Hikkim road (SNSB-BSPG 2020 XCIX 17). (6) Plagiostoma? sp. B. Strongly crushed single valve with remains of shell from the lower member at Langza (SNSB-BSPG 2020 XCIX 35). (7) Plagiostoma? sp. A. a, b, Fragmented left internal mould with remains of the inner shell layer from the Ferruginous Oolite Formation near Zangla (SNSB-BSPG 2020 XCIX 36). (8) Trigonia? sp. Right internal mould from the top of the Ferruginous Oolite Formation at Zangla (SNSB-BSPG 2020 XCIX 24). (9) Vaugonia (Orthotrigonia) sp. Poorly preserved right valve from the lower member at Langza (SNSB-BSPG 2020 XCIX 25). (10 - 13) Pruvostiella (Pruvostiella) hermanni (Oppel, 1863). 10. Hinge of left valve from the lower member close to the pass to Tashigeng; Aa, anterior adductor scar; Apr, anterior pedal retractor scar (SNSB-BSPG 2020 XCIX 54 b). 11. Hinge of left valve from the lower member at the Kaza-Hikkim road cut; Cpr, central pedal retractor scar (SNSB-BSPG 2020 XCIX 59). 12. Hinge of right valve from the lower member close to the pass to Tashigeng; Apr, anterior pedal retractor scar. a, lateral view; b, dorsal view (SNSB-BSPG 2020 XCIX 54 b). 13. Articulated specimen from the lower member at Langza (SNSB-BSPG 2020 XCIX 59 a). a, left valve view; b, dorsal view.