Exelissa aff. strangulata (d’Archiac, 1840)

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 : 20-21

Exelissa aff. strangulata (d’Archiac, 1840)

( Figs 60 A–E, 61–63 )

aff. 1843 Cerithium strangulatum d’ Archiac – p. 382, Pl. 31, Fig. 4.

aff. 1913 Exelissa strangulata (d’Archiac, 1840) – COSSMANN, p. 116, pl. 5, Figs 42–45.

Material – Five poorly preserved specimens are available on a naturally prepared rock surface; they seem to be outer casts of shells.

Measurements – Inv. No.: BHU 2020I 300 (B in Fig. 60 ); H dam. = 8.4 mm; Inv. No.: BHU 2020I 301(D in Fig. 60 ); H dam. = 7.4 mm; Inv. No.: BHU 2020I 302 (F in Fig. 60 ); H dam. = 10.6 mm.

Description – The specimens are rather high and consist of an acute early teleoconch, followed by cylindroconoidal later shell parts. Last whorl is downward and adaxially inclined. In latest growth phase, parietal and columellar lips are detached from the base and grown leftward beyond shell axis. Sparse, orthocline and straight, suture to suture ribs (six ±1) give the transverse ornament; no trace of spiral ornament can be observed on the shells, neither growth lines are visible.

Remarks – The appearance of the shells are reminiscent of the type species and to Exelissa ? sp. (see below). However, the specimens of Exelissa aff. strangulata are slenderer with suture to suture ribs that are more marked than in E. strangulata , and seemingly lack any kind of spiral ornament. These differences could be specific distinctive characters but shells are necessary for a more reliable identification.

Occurrence – Khadir Island, Ghadada Formation, Lower Callovian

Exelissa ? sp.

( Figs 64–65 )

Material – A single specimen, combination of imprint and cross section of whorls on a broken rock surface.

Measurements – Inv. No.: BHU 2020I 303; H dam. = 4.2 mm.

Description – The remnants indicate a pupiform/bottle shaped, moderately turriculate shell. Its earliest preserved part shows a single whorl with rounded surface, perhaps it is (part of) the protoconch then two whorls of pagodiform outline with a keel on their angulation follow. From the third preserved whorl, a second keel also appears subsuturally; subsequently the whorls remain convex but lose their pagodiform nature. The bicarinate whorl surface lasts to the latest preserved whorl (? last whorl); two new spiral threads also develop on this shell part, one between the primary carinae and another one just above the suture. Together with the second carina, straight, prosocline ribs also appear and extend from suture to suture. Estimated number of these ribs is six (±1) per whorl. The ribs are aligned to each other on the neighbouring whorls; their rows are prosocline on the early teleoconch and form apparently twisted ridges around the axis then become more or less orthocline. Remains of the base show several spiral threads as ornament. No growth lines are observable.

Remarks – The genus name Exelissa ? seems to approach the right systematic place of this species. However, the rather low spire with pupiform shell outline and “twisted” shell parts in early growth stage occurs also in Cryptaulax or in Xystrella . Well preserved material with protoconch and peristome is needed to find the correct generic position.

Occurrence – Ler, Chari Formation, Callovian.

Figures

Figs 60–66. Caenogastropods 2. – Fig. 60. A piece of naturally prepared bed plane with a fossil assemblage, containing also new species for the Kachchh Callovian fauna; letters indicate position of the gastropod specimens. – Figs 61–63. Exelissa aff. strangulata (d’Archiac, 1840). – 61. Apertural view, ×4.4. – 62. Abapertural view, ×5. – 63. Apertural view, ×3.5. – Figs 64–65. Exelissa? sp, ×8.8. – 64. The original view on another broken rock surface. – 65. A variety of Fig. 64, to make it more digestible through reflection, and inversion of colour. – Fig. 66. Cerithioidea? sp., a poorly preserved specimen, indicating a siphonostomatous species,also new for the Callovian fauna of Kachchh, ×3.4