Spondylopecten (Plesiopecten) subspinosus (Schlotheim, 1820)

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

Spondylopecten (Plesiopecten) subspinosus (Schlotheim, 1820)

Plate 4, fig. 3

1820 Pectinites subspinosus - Schlotheim: 223.

1938 Plesiopecten subspinosus (Schlotheim) - Weir: 50, pl. 3, fig. 18.

1952 Chlamys (Plesiopecten) subspinosa (Schlotheim) - Cox: 18, pl. 1, figs 9-12.

1995 Spondylopecten (Plesiopecten) subspinosus ( Schlotheim 1820) - Jaitly et al.: 194, pl. 18, figs 14-15.

Material.

One composite mould of a right valve and one external mould from the upper part of the lower member at the Hikkim-Kaza road (SNSB-BSPG 2020 XCIX 23).

Description.

Specimens small (H: 5.4 mm; K: 5.8 mm), suborbicular, equilateral, weakly inflated. Auricles large, distinctly separated from disk, anterior one incomplete. Surface of composite mould covered with 11-13 positive radial structures interpreted herein as corresponding to radial ribs, which are angular and show a tendency to bifurcate towards the ventral margin.

Remarks.

Despite the poor preservation of the specimens (lack of shell), they can be safely assigned to S. (Plesiopecten) subspinosus , based on the number and angularity of their ribs (compare Johnson 1984, p. 84).

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.