Chartronella belaensis, Szabó & Jaitly, 2019

Szabó, János & Jaitly, Anand Kumar, 2019, Additional Middle Jurassic gastropods from Kachchh (western India) in the collections of the Banaras Hindu University (Varanasi, India), Fragmenta Palaeontologica Hungarica 36, pp. 3-30 : 8-10

Chartronella belaensis n. sp.

( Figs 12–16)

Type specimens – Holotype Inv. No.: BHU 2020I 3.

Type locality – Bela Island , Kachchh, western India .

Type strata – Chari Formation, Callovian.

Derivation of name – From the name of the type locality.

Diagnosis – Low spired shell of rapidly expanding whorls. Suture deeply impressed. Last whorl tricarinated with markedly concave interspaces. Lowermost carina hidden on former whorls under suture in deep furrow. Last whorl downward deviating near final peristome, being strongly prosocline and slightly thickened.

Material – Single, fragmentary, and strongly worn specimen; a part of the peristome and large connected parts are lacking from the base.

Measurements – Inv. No.: BHU 2020I 3; H dam. = 5.5 mm, D dam. = 8.8 mm, pleural angle: 102°.

Description – The specimen on hand represents a low spired species with a tricarinate last whorl and a strongly convex, anomphalous base, having slightly convex wall. Between pairs of the carinae, deep, concave belts are formed. The lowermost carina is overlapped on the spire whorls by the suture and the accompanying uppermost carina. The suture itself seems rather deeply impressed. The adapical concave belt widened and the last whorl considerably deviated abapically in the last growth phase so the latest peristome became extremely prosocline. The remnants indicate its subcircular shape; the preserved parietal and basal peristome parts are slightly thickened internally.

A small area of the outer face on the last whorl preserved the ornament of very thin, rather sparse spiral threads.

Remarks – In spite of the poor preservation, the specimen well shows some characters, which distinguish it from the formerly published Chartronella species. The Bathonian Trochus obtusus Rigaux et Sauvage, 1869 is the most similar to the Kachchh specimen. It has also a rather low spire, comparable size, a blunt apical region and an ornament of delicate spiral threads, however, the interspaces between pairs of the carinae are much less concave; the carinae themselves are much weaker than in Chartronella belaensis n. sp.

Occurrence – Bela Island, Chari Formation, Callovian.