Cryptoptyxis spinosus Gründel & Nützel, 2024, sp. nov.

Cryptoptyxis? spinosus sp. nov. Plate 9: fig. 5 Etymology. Latin spinosus – thorny; because of the thorn-like extension of the axial ribs of the last whorl. Holotype. SNSB-BSPG 2016 XXI 1824. Paratypes. 2 juvenile specimens, SNSB-BSPG 2016 XXI 1825 –1826. Type locality and stratum. Upper Jurassic (Kimmeridgian) reefal limestones from the locality Saal near Kelheim, Lower Bavaria (Gründel et al. 2015, 2022). Diagnosis. Early whorls with 5 narrow axial ribs that form rib strands running across the shell i. e., ribs are aligned over consecutive whorls; last whorl with axial ribs that terminate adapically in thorn-like extensions; a spiral sculpture could not be seen with certainty. Description. Shell trochiform, conical, higher than wide, with last whorl higher than spire; largest specimen 22 mm high; whorls low; whorl face with straight; suture shallow but distinct; ornament consists of 5 axial ribs per whorl; axial ribs sharp, high and very narrow with a weak cusp at adapical end; axial ribs extend from adapical suture to center of base; ribs of last whorl of illustrated specimen increase significantly in height and terminate adapically in a thorn-like tip; ribs on spire whorls aligned to each other from whorl to whorl, only slightly offset from one another, forming rib strands that run weakly prosocline across shell; spiral cords or lirae absent (due to preservation?); only occasionally three faint cusps visible on crest of axial ribs that could indicate presence of spiral ornamentation; aperture not preserved. Remarks. Cryptoptyxis rarenodosa Gründel et al., 2019 has a ramp, but above all, the entire shell is covered with strong spiral cords. Other similar species (e. g., Cryptoptyxis sp. sensu Hägele (1997) from the Upper Jurassic; Cerithium quinquangulare Hébert and Eudes-Deslongchamps, 1860, Callovian) lack the adapical extensions of the axial ribs on the last whorl. Cryptoptyxis? fortiter Gründel et al., 2022 has distinct spiral cords with nodes at the intersections with the axial ribs. In this species, the nodes on the subsutural spiral cord are strongly enlarged on the last whorl, but the ribs do not have an adapical extension.