Aphanoptyxis sinerugae sp. nov.

Plate 12: figs 1–3

Etymology.

Latin sine rugae – without folds, because of the lack of plaits or folds within the whorls.

Holotype.

SNSB-BSPG SNSB-BSPG 2016 XXI 1891.

Paratypes.

Saal, 2 specimens, SNSB-BSPG 2016 XXI 1892 –1893.

Type locality and stratum.

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

Diagnosis.

Shell moderately slender, cyrtoconoid, apical angle decreases during ontogeny; whorl face strongly concave, without ornament; suture situated on ridge formed by two adjacent whorls; a siphonal canal appears to have formed; whorls without plaits or folds.

Description.

Shell slender, cyrtoconoid, apical angle decreases during ontogeny; holotype 98 mm high; suture situated on ridge formed by two adjacent whorls; whorl face strongly concave, without ornament except of occasionally weakly reinforced growth lines; growth lines on whorl face orthocline and almost straight, bent strongly backwards below adapical suture; base slightly convex, smooth with weakly prosocyrt growth lines, phaneromphalous; transition from whorl face to base at sharp edge forming almost right angle; aperture rhomboid mouth, seemingly with siphonal canal, without plaits or folds.

Remarks.

Nerinea turbatrix Loriol in Loriol and Bourgeat (1886–1888) has a more slender shell, its shape is not cyrtoconoid and its whorls are higher. Cossmannea (Eunerinea) ursicina (Thurmann) sensu Fischer and Weber (1997) has a distinct spiral sculpture. Umbonata dilatata (d’Orbigny) sensu Fischer and Weber (1997) is more slender, the whorls are lower and 3 plaits are formed in the aperture. Nerinea arduennensis Buvignier, 1852 is more slender, the whorls are lower, the shell shape is not cyrtoconoid, and several plaits are present. Cryptoplocus engeli Geiger, 1901 has lower and less concave whorls and a strong columellar plait. Nerinea castor d’Orbigny sensu Maire (1926) has no cyrtoconoid shell shape, and plaits have not been reported for it (according to d’Orbigny 1851 and Fischer and Weber 1997, several plaits are formed).