Pruvostiella Agrawal, 1956a

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

Genus Pruvostiella Agrawal, 1956a

Emended diagnosis.

Equivalve, inequilateral shell, generally longer than high, thick-shelled. Inner shell margin crenulated; umbonal area depressed and ornamented with spaced, well-developed, commarginal ribs asymmetric in cross-section; remaining shell smooth except for growth lines. Hinge with serrated teeth. Right valve with 2-3 cardinals and 1 anterior and 1 posterior lateral. Left valve with 2-3 cardinals and 1 anterior and 1 posterior lateral. Distinct pedal retractor muscle scar developed below the hinge line and close to the anterior adductor muscle scar. Inner shell margin crenulated.

Remarks.

Pruvostiella was erected by Agrawal (1956a: 435) as a subgenus of Neocrassina for specimens from the Oxfordian Dhosa Oolite of Kachchh, western India. The main diagnostic feature of his new subgenus is the umbonal region, which is distinctly depressed, with small beaks and ornamented with spaced, well-developed commarginal ribs, which are asymmetric in cross-section with a steeper slope dorsally. The ribs fade after 10-15 mm to be replaced by irregular growth lines. Agrawal (1956a) included a number of astartids in Pruvostiella (Table 3 ). Pruvostiella is here elevated to generic rank.

Fürsich et al. (2000: 92; 2019, p. 174) created Eoseebachia as a subgenus of Seebachia Holub & Neumayr, 1881 and accommodated Astarte major J. de C. Sowerby, 1840 and their new species Seebachia elongata in this subgenus. Although these species are related to Seebachia , they are clearly more closely related to Pruvostiella , as the former genus is strongly elongated, wedge-shaped and has a distinct posterior umbonal ridge. Eoseebachia is, therefore, moved from Seebachia to Pruvostiella .

Gardner and Campbell (2002, p. 328) regarded Pruvostiella as a junior synonym of Neocrassina Fischer, 1886, a view not followed here. The depressed, flattened umbo, the corresponding distinct break in the growth spiral of the shell, and the distinctly serrated cardinal teeth are consistent features of many large astartids from the Ethiopian faunal province (Table 3 ).

Pruvostiella (Pruvostiella) appears to be restricted to the Callovian-Oxfordian time interval of the Ethiopian Faunal Province (Madagascar, East Africa, India) and possibly occurs also in the Kimmeridgian of New Zealand (Trechman 1923; Marwick 1953), whereas Pruvostiella (Eoseebachia) occurs from the Late Oxfordian to the Late Tithonian (and probably earliest Cretaceous) in the same area (e.g., Dietrich 1933; Cox 1965). Eoseebachia differs from Pruvostiella s.s. by being up to three times larger, generally more elongated and by having a lunule with a lower length-width ratio.

J. de C. Sowerby (J. de C. Sowerby, 1840, pl. 61, fig. 1) erected Astarte major for the large astartids from the Upper Jurassic of Kachchh. Blanford (1864), Stoliczka (1866), and Holdhaus (1913) regarded moderately-sized astartids from the Himalayas also as Astarte major J. de C. Sowerby, 1840. Whereas Blanford (1864, p. 135, …” undoubtedly identical") was quite confident, Holdhaus only tentatively regarded the large astartids from Spiti to belong to Sowerby’s Astarte major from Kachchh. Holdhaus (1913) erroneously regarded that Sowerby’s name was preoccupied by Astarte elegans major Zieten (1833: 82, pl. 62, fig. 1). Therefore, Holdhaus (1913, p. 443) erected the replacement name Astarte sowerbyana for the forms from the Himalayas and Kachchh. It is clear that the Kachchh species differs from the Spiti material. The specimens from the Spiti Shale are placed herein in P. (Pruvostiella) hermanni (Oppel, 1863). The large astartid from Kachchh represents Sowerby’s A. major and the species is assigned to Pruvostiella (Eoseebachia) , because it is much closer to Pruvostiella than to Seebachia (see above). Thus, in the Kachchh Basin four species of Pruvostiella occur: P. (Eoseebachia) major (J. de C. Sowerby, 1840), P. (Eoseebachia) elongata Fürsich, Heinze & Jaitly, 2000, P. (Pruvostiella) unilateralis (J. de C. Sowerby, 1840), and P. (Pruvostiella) freneixae Agrawal, 1956a. In the Himalayas, in contrast, the species group is represented by P. (Pruvostiella) hermanni (Oppel, 1863).