Eucyclus sp.

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 : 376

Eucyclus sp.

Fig. 17A .

Material.— One specimen: MNHNL GL205 , Luxembourg Sandstone Formation , Hettangian–Lower Sinemurian, exact locality and stratigraphical level unknown .

Dimensions.—See Table 2.

Description.—Shell large, turbiniform with strongly impressed suture. Whorls strongly convex, angulated at the periphery. Angulation at about middle of the whorl. Base distinctly convex, anomphalous. Aperture semicircular, angular at the termination of the periphery on the outer lip and slightly elongated at the base of the columella. Peristome seemingly discontinuous at the parietal lip. Columellar lip straight and subvertical. Ornament mainly consisting of strong spiral cords. Periphery marked by a spiral keel bearing widely spaced and robust nodes, about twelve on the last whorls. Base ornamented with six strong spiral cords. The spiral cord below the peripheral keel bears low nodes. The other spiral cords of the base are slightly nodose or wavy. The nodes on the peripheral angulation and on the spiral cords of the base are roughly aligned to each other in axial direction, seemingly formed by intersection of the spiral ornament with low and feeble collabral wrinkles. Weak traces on the inner mould of two spiral cords on the ramp. Growth lines strong, forming a pattern of dense threads which make strongly rough the interspaces between the spiral cords.

Remarks.—The shell is only preserved on the last whorl of the present specimen. Another whorl is preserved on the internal mould and the apex is missing. Shape and ornament are typical for the genus Eucyclus Eudes−Deslongchamps, 1860 . Moreover, the external ornament is partly reflected on the inner mould surface which is a characteristic feature of the members of the family Eucyclidae Koken, 1897 (e.g., Conti and Monari 1991: pl. 8: 10–18; 1995: pl. 2: 12–14; 2001: fig. 8, 15; Szabó 1995: pl. 7: 13). The general habitus and especially the large size of the shell distinguish the specimen from other coeval Eucyclus species. However, its very poor preservation prevents more detailed comparisons.

Figures

Fig. 17. Eucycloidean gastropos from Luxembourg Sandstone Formation, Early Jurassic. A. Eucyclus sp., MNHNL GL205, apertural (A1), basal (A2) and dorsal (A3) views, Hettangian–Early Sinemurian, exact locality and stratigraphical level uncertain. B–E. Brouch (Mersch, Grand−Duchy of Luxembourg), Late Hettangian (Schlotheimia angulata Zone, Schlotheimia complanata Subzone). B, C. Spirocirrus weisi sp. nov., B. Holotype, MNHNL BR299, lateral view (B1) and detail of the ornament (B2). C. Paratype, MNHNL BR374, apertural (C1) and subdorsal (C2) views. D, E. Platyacra aff.sinistrorsa (Terquem, 1855). D. MNHNL BR373, dorsal view (D1) and detail of the ornament of the base (D2). E. MNHNL BR876, dorsal (E1), subapertural (E2), and basal (E3) views, and detail of the apical spire (E4).