Neritopsis? rotundatus, Gründel & Nützel, 2024

Gründel, Joachim & Nützel, Alexander, 2024, Late Jurassic (Upper Kimmeridgian) gastropods from Saal near Kelheim (Germany, Bavaria), Zitteliana 98, pp. 19-72 : 19-72

Neritopsis? rotundatus sp. nov.

Plate 6: figs 8–12

2017 Metriomphalidae n. gen.? sp. 1 – Gründel, Keupp and Lang: 203, pl. 15, figs 8–13.

Etymology.

Latin rotundatum – rounded (because of the round shell shape).

Holotype.

SNSB–BSPG 2016 XXI 1767 (Plate 6 : figs 8–12).

Paratypes.

5 specimens from Saal. SNSB–BSPG 2016 XXI 1768 –1772.

Type locality and stratum.

Upper Jurassic (Kimmeridgian) reefal limestones from the locality Saal near Kelheim, Lower Bavaria ( Gründel et al. 2015, 2022).

Diagnosis.

Shell neritiform, low-spired with large last whorl that is evenly convex (from adapical suture to the center of the base) and evenly covered with more than 15 spiral cords; spiral cords are about as wide as spiral furrows separating them; spiral cords entirely covered with small nodes; axial ribs absent; no callous formations visible in apertural area.

Description.

Shell neritiform, holotype (largest specimen) 14 mm wide and high;

late whorls strongly and evenly convex (including base); in some specimens, a spiral cord is reinforced near adapical suture, slightly angulating whorl face and delimiting a ramp with several spiral cords; first recognizable sculpture consists of 4–6 spiral cords lacking nodes; cords almost equally strong or alternation of stronger and weaker cords; further spiral cords evenly cover whorl face and base; holotype has 18 spiral cords from adapical suture to center of base; during growth, spiral cords become equal in strength; numerous small, densely packed nodes present on spiral cords of last whorl; nodes have deep pit in apertural direction, thus resembling short hollow spines; axial ribs absent, only weakly reinforced growth lines can be seen in spiral furrows; whorl face and base evenly rounded; base anomphalous; aperture broadly oval, slightly tapering adapically and widely rounded abapically; callous formations lacking.

Remarks.

Neritopsis buchini Guirand & Ogérien, 1865 has fewer spiral cords, the spiral cords are wider than the separating grooves, the tubercles are less numerous and not as distinct. Neritopsis buchini sensu Loriol in Loriol and Bourgeat (1886–1888) also has fewer spiral cords. The spiral cords of Neritopsis buchini are significantly narrower than the spiral grooves separating them and there are fewer nodes on the spiral cords. Neritopsis imbricata Étallon sensu Loriol in Loriol and Bourgeat (1886–1888) has a more inflated last whorl, the nodes on the spiral cords are smaller and more numerous. Neritopsis imbricata sensu Zittel (1873) has a more transversely elongated shell shape, the outer lip of the aperture is strongly asymmetrically convex with the periphery is low on the whorls. Nerita goldfussi Keferstein sensu Goldfuss, (1844) is adapically flattened with a sunken apex and fewer spiral cords of variable thickness. The aperture of Neritopsis ? rotundatus n. sp. seems to be asymmetrical and not symmetrical as would be typical for the genus Neritopsis (see Kaim and Sztajner 2005).

Figures

Plate 6. (1, 2) Parvulatopsis? sp. 1, SNSB – BSPG 2016 XXI 1759, lateral and apical views, width 12 mm. (3) Neridomus hemisphaerica (Roemer, 1836), SNSB – BSPG 2016 XXI 1764, lateral view, width 33 mm. (4, 5) Neridomus hemisphaerica (Roemer, 1836), SNSB – BSPG 2016 XXI 651, lateral views, height 35 mm. (6, 7) Neridomus hemisphaerica (Roemer, 1836) with color pattern, SNSB – BSPG 2016 XXI 1765, lateral and apical views, width 36 mm. (8–12) Neritopsis? rotundatus sp. nov., holotype, SNSB – BSPG 2016 XXI 1767, (8–10) abapertural, apertural and apical views, width 15 mm, (11) detail in oblique apical view, width 11 mm, (12) basal view, width 15 mm. (13, 14) Wallowiella (Plicaropsis) cancellata (Stahl, 1824) (adult), SNSB – BSPG 2016 XXI 1773, lateral and basal views, width 21 mm.