Camptonectes (Camptochlamys) obscurus (J. Sowerby, 1818)

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

Camptonectes (Camptochlamys) obscurus (J. Sowerby, 1818)

Plate 3, fig. 13

Pecten obscura *1818 Pecten obscura - J. Sowerby: 3, pl. 205, fig. 1.

Camptonectes indicus 1852 Camptonectes indicus sp. nov. - Cox: 25, pl. 3, figs 1-4.

Camptonectes Germaniae ?1939 Camptonectes Germaniae ( d’Orb.) - Stefanini: 171, pl. 19, fig. 11.

1956 Camptonectes indicus Cox - Agrawal: 77, pl. 9, fig. 5.

1968 Camptonectes indicus Cox - Maithani: 505, pl. 33, fig. 6.

1979 Camptonectes (Indonectes) obscurus (J. Sowerby) subgen. nov. - Kanjilal: 120, fig. 6.

1983 Camptonectes (Indonectes) obscurus (J. Sowerby) - Singh and Jaitly: 47, pl. 1, fig. 5.

1995 Camptonectes (Camptochlamys) obscurus (J. Sowerby, 1818) - Jaitly et al.: 196, pl. 19, figs 7-8.

Material.

A single left valve partly in shell preservation, seen from the interior, from the lower member near the pass to Tashigeng (SNSB-BSPG 2020 XCIX 13).

Description.

Shell suboval, higher than long (H: 22.2 mm, L: ~20 mm), moderately inflated, anteroventral, posteroventral and ventral margins rounded and regularly curved; antero- and posterodorsal margins of disc sub-straight. Anterior auricle large, distinctly set off from anterodorsal flank, which is more steeply sloping than posterodorsal flank. Tip of umbo and posterior auricle missing, anterior and posterior margin of disc also not fully preserved. Disc ornamented with thin, sharp, regularly spaced commarginal ribs and numerous thin divaricate radial grooves, separated by smooth, flat intervals about twice the width of the grooves. Umbonal area with thin radial riblets. Anterior auricle covered with spaced commarginal riblets intersected by thin radial riblets, creating a reticulate pattern.

Remarks.

The specimen closely corresponds to the diagnosis of Camptonectes (Camptochlamys) obscurus as given by Johnson (1984). So far, the species has not been recorded from the Himalayan shelf of the southern Tethys, but it occurs in the Callovian of the Kachchh Basin further south ( Cox 1952; Jaitly et al. 1995) and possibly also in other parts of the Ethiopian faunal province (e.g., as Camptonectes germaniae ( d’Orbigny, 1850) in Somalia; Stefanini 1939 p. 171, pl. 19, fig. 11).

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).