Bactroptyxis cf. fasciata (Voltz, 1836)

Gruendel, Joachim, Keupp, Helmut, Lang, Fritz & Nuetzel, Alexander, 2022, Late Jurassic (Upper Kimmeridgian) Heterobranchia (Gastropoda) of the coral-facies of Saal near Kelheim and the viciniy of Nattheim (Germany), Zitteliana 96, pp. 179-221 : 179

Bactroptyxis cf. fasciata (Voltz, 1836)

Plate 13: figs 3-5

?1836 - Nerinea fasciata Voltz - Bronn: 554, pl. 16, fig. 21.

Material.

One specimen (SNSB-BSPG 2021 XV 56) and one questionable specimen, both from Saal, collection Lang.

Description.

The bona fide specimen is 36 mm high. The shell is very slender. The whorl face is straight. The sutures are not impressed and only occasionally visible. The ornament is only preserved on the last whorl. It consists of four spiral cords of equal strength that are equally distant from each other. A knobby ornament is absent. An abapical spiral cord, probably representing the bordering spiral cord, is visible above the suture and marks the angular transition to the flat base. Only the inner lip of the aperture is preserved; it shows one parietal plait and two columellar plaits.

Remarks.

Nerinea fasciata sensu Bronn (1836) has the same shell shape as the present species and it has also four spiral cords, which are, however, of unequal strength.

Relationships.

Bactroptyxis teres ( Münster in Goldfuss, 1844) differs from Bactroptyxis cf. fasciata by having four strong spiral cords of equal strength and at equal distances. Bactroptyxis teres ( Münster) sensu Hägele (1997) has more and weaker spiral cords of unequal strength. Aptyxiella rupellensis d’Orbigny sensu Pchelintsev (1965) has higher whorls and more spiral cords. Aptyxiella inornata d’Orbigny sensu Maire (1913) has five spiral cords on the whorl face and a subsutural bulge; apertural plaits are not visible. Nerinea quadricincta Münster sensu Maire (1913, pl. 11, fig. 7) has two stronger spiral cords on the whorl face (unlike in Maire’s 1913, p. 93 description) and allegedly additional weak spiral cords that are unrecognizable, and it shows swellings near the sutures. These swellings form bulges on which the sutures are situated.

Figures

Plate 13. (1 - 2) Bactroptyxis teres (Muenster in Goldfuss, 1844), from the Nattheim area (collection Sauerborn); (1) last whorl with aperture, height 11 mm; (2) lateral view, height 29 mm. (3 - 5) Bactroptyxis cf. fasciata (Voltz, 1836), SNSB-BSPG 2021 XV 56, Saal (collection Lang); (3) detail of ornament, width 4.5 mm; (4) lateral view, height 36 mm; (5) aperture, width of whorl 4.6 mm. (6 - 8) Bactroptyxis? subcochlearis (Muenster in Goldfuss, 1844). (6 - 7) SNSB-BSPG 2021 XV 57, Saal (collection Neubauer); (6) detail of ornament, height 11.5 mm; (7) lateral view, height 55 mm. (8) SNSB-BSPG 2021 XV 58, Saal (collection Lang), lateral view, height 29 mm. (9 - 10) Bactroptyxis? tricincta (Muenster in Goldfuss, 1844). (9) SNSB-BSPG 2021 XV 52, Saal (collection Lang), lateral view, height 48 mm (original to Gruendel 2017, fig. 14 B). (10) SNSB-BSPG 2021 XV 52, Saal (collection Lang), detail of shell in lateral view, height 21 mm. (11 - 16) Bactroptyxis? tricincta (Muenster) sensu Quenstedt (1881 - 1884). (11 - 12) Collection University Tuebingen (collection Quenstedt); Nattheim, lateral views, height 29 mm (original to Quenstedt 1881 - 1884, pl. 207, fig. 9). (13) SNSB-BSPG 2021 XV 53, Saal (collection Lang), lateral view, height 64 mm. (14) SNSB-BSPG 2021 XV 54, Saal (collection Lang), lateral view, height 55 mm. (15 - 16) SNSB-BSPG 2021 XV 55, Saal (collection Lang); (15) lateral view, height 72 mm; (16) last whorl, width 17 mm.