Sulcoactaeon? haboensis, 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 : 25-28

Genus? Sulcoactaeon Cossmann, 1895

Type species – Actaeonina striatosulcata Zittel et Goubert, 1861

Sulcoactaeon? haboensis n. sp.

( Figs 80–83)

Type specimen – Holotype Inv. No.: BHU 2020I 310.

Type locality – Habo Dome.

Type strata – Patcham Formation, Bathonian.

Derivation of name – Refers to the locality.

Diagnosis – Bulliniform shell with single visible whorl of coaxial protoconch, and teleoconch whorls, having narrow, concave, subsutural ramp with sharp rim. Aperture elongated, leftward extending beyond axis in basal region. Peristome interrupted but thin inductura smoothen parietal wall. Outer and basal lip outward tapering. Columellar/umbilical lip arched and externally sharply angular; its widened inner surface hidden in normal apertural view since nearly perpendicular to plane of peristome. Hidden part having median furrow, possibly containing also narrow opening of umbilicus at its adapical end. Whole teleoconch, excepting ramp, ornamented by sparse spiral striae with ribbons in interspaces; few differently strong threads occurring along and on external part of columellar/umbilical lip.

Material – Single, rather well-preserved specimen.

Measurements – Inv. No.: BHU 2020I 310; H = 5.5 mm, D = 3.1 mm.

Description – A minute, ovate shell of 4.5 visible whorls with impressed suture represents this species. The first whorl, which that is almost planispiral, convex and seemingly smooth, yet belongs to the protoconch, which is apparently coaxial with the teleoconch. A marked growth line indicates beginning of the teleoconch, which has a narrow, slightly concave ramp with a clear angulation as abaxial rim. The convex outer face of the whorls turns into the convex base without boundary. The peristome and aperture are subaxially elongated and extend higher than half of the full shell and have left side concave water drop shape. The outer lip is thin, outward tapering and smoothly arched to the basal lip, which continues as a sharp outer rim of the columellar/umbilical lip then terminates at the parietal wall. Major part of the columellar lip is hidden behind the sharp frontal edge; it is rather wide and nearly perpendicular to the plane of the peristome; in axial direction, it is slightly concave adaperturally, and has also a vertical furrow, perhaps with a narrow opening for a possible umbilicus. No trace of columellar or parietal folds is observable.

The first whorl, which belongs to the protoconch is smooth but, excepting the ramp, the teleoconch is sparsely striated along its full length; the striae separate nearly equally wide ribbons. Other ornament appears only on and along the outer rim of the columellar/umbilical lip as differently strong spiral threads of inequal length. The growth lines have nearly orthocline orientation and asymmetrically prosocyrt shape; near the ramp, their arch is narrower than elsewhere. Growth lines of the ramp are opisthocline and opisthocyrt.

Remarks – The striae of the shell are filled by unremovable sediment. However, short rim pieces of the ribbons show subregular undulations that may indicate pitted nature of the striae.

The species of Sulcoactaeon have frontally exposed columellar or umbilical lip and in this feature, they differ from the Kachchh specimen that has a new type of inner lip. It remains a question whether this inner lip bears only species or even generic level distinctive meaning; that is why the question mark is added to the genus name.

Occurrence – Habo Dome, Patcham Formation, Bathonian.