Australobuchia spitiensis (Holdhaus, 1913)

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

Australobuchia spitiensis (Holdhaus, 1913)

Plate 3, fig. 3

*1913 Aucella spitiensis n.sp. form. typ. - Holdhaus: 410, pl. 97, fig. 8-11.

?1913 Aucella spitienis grandis nov. form. - Holdhaus: 411, pl. 97, fig. 7.

?1913 Aucella spitiensis superba nov. form. - Holdhaus: 411, pl. 97, fig. 13.

?1913 Aucella spitiensis extensa nov. form. - Holdhaus: 411, pl. 97, fig. 12.

1959 Buchia spitiensis (Holdhaus) - Fleming: 898, figs 15, 16, 20C, D

1976 Buchia spitiensis (Holdhaus) - Wen: 85, pl. 21, fig. 1.

1976 Buchia spitiensis (Holdhaus) - Gu et al.: 151, pl. 46, figs 3-7.

1988 Buchia spitiensis Holdhaus 1903 - Li and Grant-Mackie: 253, fig. 2A, B.

Material.

Composite moulds of one articulated and one right valve and external moulds of fragments of one right and one left valve from the middle member, roadside close to Komic (SNSB-BSPG 2020 XCIX 43) and from the upper member close to Demul Pass (SNSB-BSPG 2020 XCIX 43).

Description.

Poorly preserved composite and external moulds, some with remains of shell, obliquely elongated, higher than long (H: 25.8 mm, L: 23.1 mm). Mould of right valve moderately inflated, with distinctly sloping anterior and posterior flank and inconspicuous umbo; mould of left valve strongly inflated, umbo prominent, beak incurved, prosogyrate. Anterior and posterior margins sub-parallel, weakly convex, ventral margin strongly convex. Surface covered with numerous growth folds of varying strength. Anterior auricle of right valve concave, tongue-like, not level with commissure but directed slightly towards left valve.

Remarks.

Most specimens are strongly flattened and fragmentary so that diagnostic features are difficult to observe. Australobuchia spitiensis as described by Holdhaus (1913) varies considerably in outline and degree of obliquity. Holdhaus (1913) distinguished altogether four varieties (forma Australobuchia spitiensis typica , forma Australobuchia spitiensis grandis , forma Australobuchia spitiensis extensa , and forma Australobuchia spitiensis superba ). Due to the limited information from the present specimens, we cannot evaluate these varieties. Our material corresponds most closely to his forma Australobuchia spitiensis typica . The species is also common in the Mt. Everest region (e.g., Wen 1976).

Figures

Plate 3. (1, 2) Bositra buchii (Roemer, 1836). Composite moulds from the lower member at Langza. 1. a, articulated specimen in butterfly position, dorsal view (SNSB-BSPG 2020 XCIX 18 a); b, c, single valves, lateral view (SNSB-BSPG 2020 XCIX 18 b). 2. External mould of right valve (SNSB-BSPG 2020 XCIX 19). (3) Australobuchia spitiensis (Holdhaus, 1913). Composite mould of articulated specimen from the middle member, roadside close to Komic; right valve view (SNSB-BSPG 2020 XCIX 43). (4 - 5) Australobuchia blanfordiana (Stoliczka, 1866). upper member close to Demul Pass. 4. Right valve (SNSB-BSPG 2020 XCIX 46). 5. Right valve (SNSB-BSPG 2020 XCIX 45). (6 - 10)? Malayomaorica sp. upper member close to Demul Pass. 6. Left valve (SNSB-BSPG 2020 XCIX 51 a). 7. Right valve interior (SNSB-BSPG 2020 XCIX 52). 8. Fragment of right valve (SNSB-BSPG 2020 XCIX 51 b). 9. Left valve (SNSB-BSPG 2020 XCIX 51 c). 10. Fragment of right valve (SNSB-BSPG 2020 XCIX 51 d). (11) Entolium (Entolium) corneolum (Young & Bird, 1822). Internal mould of a left valve from the lower member at Langza (SNSB-BSPG 2020 XCIX 15). (12) Propeamussium (Propeamussium) sp. Internal mould of a small fragment from the lower member at Langza (SNSB-BSPG 2020 XCIX 12). a, natural size; b, enlarged. (13) Camptonectes (Camptochlamys) obscurus (J. Sowerby, 1818). Left valve interior from the lower member near the pass to Tashigeng (SNSB-BSPG 2020 XCIX 13).