Bandelopsis, Fryda, Blodgett, and Stanley, 2003

Monari, Stefano, Valentini, Mara & Conti, Maria Alessandra, 2011, Earliest Jurassic patellogastropod, vetigastropod, and neritimorph gastropods from Luxembourg with considerations on the Triassic-Jurassic faunal turnover, Acta Palaeontologica Polonica 56 (2), pp. 349-384 : 360-361

Bandelopsis ? cf. exigua ( Terquem, 1855)

Fig. 8A, B .

cf. 1855 Neritopsis exigua sp. nov.; Terquem 1855: 279, pl. 17: 11a, b.

?1861 Neritopsis compressula sp. nov.; Gümbel 1861: 861.

?1867 Neritopsis exigua Terquem ; Moore 1867: 547–548, pl. 15: 19.

?1893 Neritopsis compressula Gümbel ; Ammon 1893: 174–175, fig. 12.

1988 Neritopsis exigua Terquem ; Meier and Meiers 1988: 25–26, pl. 2: 5a, b.

Material.— Four specimens: MNHNL BR 300, MNHNL BR 357, MNHNL BR 700, MNHNL BR 880, Brouch, Upper Hettangian ( Schlotheimia angulata Zone , Schlotheimia complanata Subzone ).

Dimensions.—See Table 2.

Description.—Globose, relatively small−sized shell with prominent spire. Spire formed by about four rapidly expanding whorls with inner shell wall not dissolved. Early spire with relatively high, convex whorls. Last whorls bearing a spiral angulation which delimits a somewhat wide ramp. Ramp shallow, inclined and feebly convex. Suture impressed and downward shifting on the last whorl. Outer whorl face convex, with lower rim corresponding to a rounded, feeble angulation which becomes slightly exposed on the spire during the last whorl growth. Base well rounded and swollen, seemingly anomphalous or with a very narrow axial fessure. Ornament consists of collabral ribs crossed by spiral threads. Collabral ribs prosocline, strong, evenly sized and widely spaced. They tend to vanish on the ramp where they disappear before reaching the adapical suture. About ten collabral ribs on the last whorl which smoothly pass onto the base. Spiral threads of two alternating orders in the juvenile spire. They become almost equally strong on the last whorl. Last whorl sculptured with about fifteen spiral threads on the base and about ten on the ramp. The spiral threads limiting the outer whorl face are more marked than the others. Intersection between spiral threads and collabral ribs marked by granulae and by low nodes on the outer angulation of the ramp. Growth lines prosocline, prosocyrt on the spire and slightly opisthocyrt on the base.

Remarks.—The material shows similarities to Bandelopsis? exigua ( Terquem, 1855) , from the Hettangian of Hettange−Grande (Lorraine, France) in the growth rate, in the height of the spire, and in the sculpture of the ramp. However, Terquem (1855) erected the species on the basis of a single specimen partly embedded in the sediment, whose characters are hardly noticeable. This forced us to leave open the species attribution.

The specimen from the Hettangian of the Vendée (western France) ascribed by Cossmann (in Chartron and Cossmann 1902: 193, pl. 4: 29, 30) to Neritopsis exigua Terquem, 1855 shows a much more laterally compressed shell. The ornament consists of collabral riblets which are nearly as strong as the spiral threads, thus producing an evenly reticulated pattern. The specimen from the Early Sinemurian of the Peloritani Mountains (eastern Sicily, Italy) described by Lentini (1973: 61, pl. 18: 10) as N. aff. exigua has a clearly less globose shell and a much more acute and prominent spire. Moore (1867) quoted N. exigua in the lowermost Sinemurian sediments of Brocastle (Glamorganshire, United

Kingdom). However, the poor illustration and description made by that author prevent more detailed comparisons.

The specimens described here are also strongly reminiscent of Neritopsis compressula Gümbel, 1861 , a species known from the Early Jurassic sediments of the Hochfelln Mountain (Northern Calcareous Alps, Austria). They differ in the presence of a more inclined and wider ramp on the adult shell. Moreover the ramp is sculptured with a marked spiral ornament.

Stratigraphic and geographic range.—Late Hettangian ( Schlotheimia angulata Zone , Schlotheimia complanata Subzone ), Brouch ( Luxembourg);?Hettangian, Hettange−Grande (Lorraine, France);?Hettangian–earliest Sinemurian, South Wales ( United Kingdom);?Early Jurassic, Hochfelln Mountain (Northern Calcareous Alps, Austria).

Figures

Fig. 8. Neritopsoideans from Brouch (Mersch, Grand−Duchy of Luxembourg), Late Hettangian (Schlotheimia angulata Zone, Schlotheimia complanata Subzone), Early Jurassic. A, B. Bandelopsis? cf. exigua (Terquem, 1855). A. MNHNL BR880, dorsal (A1), and apical (A2) views. B. MNHNL BR700, dorsal (B1), apertural (B2), and apical (B3) views. C. Bandelopsis? sp., MNHNL BR367, apical (C1), apertural (C2), and dorsal (C3) views.