Acrostylus? sp. 1

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

Acrostylus? sp. 1

Plate 6: figs 1, 2

v2017 - Nerineoidea Nr. 1 - Gründel: 33, pl. 13, fig. 13 C.

Material.

Two specimens from Saal, collection Lang, one of which is illustrated (SNSB-BSPG 2021 XV 73).

Description.

The present material is poorly preserved and only fragmentary. The illustrated specimen is 23 mm high. The whorl face is weakly concave. The whorls are ornamented with a subsutural row of knobs and two strong, knobby spiral cords below it, followed by one or two weak spiral cords and a strong, knobby suprasutural spiral cord. The knobby sub- and suprasutural cords form a bulge on which the suture is situated. The base is flat and its transition to the whorl face is angulated. A distinct umbilicus is present. The aperture is rhomboid. It is unclear whether a siphonal canal is present. The aperture has a parietal, a columellar, and a palatal plait.

Relationships.

Nerinella subscalaris Münster sensu Schlosser (1882) has bulges that lack knobs and lacks an umbilicus. Nerinea danubiensis Zittel sensu Schlosser (1882) has lower whorls, the bulges have stronger knobs, and it lacks distinct spiral cords between the bulges. Nerinella subtricincta ( d’Orbigny) sensu Fischer and Weber (1997) has an almost straight whorl face, its bulges are weaker and only weakly knobby ( Fischer and Weber 1997, p. 54: "faiblement granuleux"). Nerinella (cf.) Nerinella laufonensis Thurmann sensu Loriol in Loriol and Koby (1895) and Hägele (1997) is slenderer and has weaker bulges. Nerinea chantrei Loriol and Nerinea ornata d’Orbigny, both sensu Loriol in Loriol and Bourgeat (1886-1888), have a slenderer shell with higher and more concave whorls. Nerinea hoheneggeri Peters sensu Zittel (1873) has a slenderer shell, more spiral cords on the whorl face between the bulges, and lacks an umbilicus. Nerinea roemeri Philippi sensu Goldfuss (1844) is slenderer, has higher whorls; its whorls are not concave and the bulges are rather weak.

Figures

Plate 6. (1 - 2) Acrostylus? sp. 1., SNSB-BSPG 2021 XV 73, Saal (collection Lang), (original to Gruendel 2017, fig. 13 C); (1) section of shell, height 23 mm; (2) lateral view, height 23 mm.