Endoplocus acutus, Gründel & Keupp & Lang & Nützel, 2022

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

Endoplocus acutus sp. nov.

Plate 7: figs 1-7

part?1898 - Phaneroptyxis clymene d’Orbigny - Cossmann: 16, questionable pl. 8, fig. 35, non pl. 1, figs 23, 24.

Derivatio nominis.

Latin Endoplocus acutus - acute; because of the acute spire.

Holotype.

SNSB-BSPG 2021 XV 14 (collection Lang).

Locus typicus.

Saal quarry near Kelheim.

Stratum typicum.

Upper Kimmeridgian.

Paratypes.

Thirteen specimens from Saal, collection Lang and Keupp: SNSB-BSPG 2021 XV 15-19, 171-178.

Additional material.

Three specimens from Saal, without type status (two specimens collection Neubauer, one specimen collection Lang).

Diagnosis.

The shell has a high, multi-whorled, acute spire; last whorl of large specimens distinctly lower than spire; last whorl somewhat constricted (slightly pupoid outline); no ornament visible.

Description.

The holotype is 29 mm high. The shell has a high, multi-whorled, acute spire. The whorls are low with a slightly convex to straight whorl face. The sutures are somewhat impressed. In some specimens, a narrow ramp accentuates the sutures. The whorls lack visible ornament. The last whorl of large specimens is slightly tapering in an abapical direction resulting in a slightly pupoid shell shape. The last whorl is distinctly lower than the spire. The transition from whorl face to the strongly convex base is fluent and evenly rounded. The base is smooth and has a distinct umbilicus that is surmounted by an indistinct cord. The aperture is narrow. The inner lip has a strong parietal and two columellar plaits. The adapical columellar plait is weaker than the abapical one.

Remarks.

The specimen illustrated by Cossmann (1898, pl. 8, fig. 35; specimens in pl.1, figs 23, 24 differ more strongly) as Phaneroptyxis clymene d’Orbigny from the Rauracien resembles Endoplocus acutus sp. nov. However, the specimen illustrated by Cossmann (1898) differs from Endoplocus acutus sp. nov. by having a slenderer shell, a higher last whorl in relation to the spire height, and by having only a single columellar plait. Fischer and Weber (1997) illustrated the holotypes of Phaneroptyxis moreana ( d’Orbigny, 1851) ( Fischer and Weber 1997, pl. 13, fig. 4) and of P. clymene ( d’Orbigny, 1851) ( Fischer and Weber 1997, pl. 13, fig. 5). These taxa were interpreted to represent a single variable species by Fischer and Weber (1997), both differ significantly from Endoplocus acutus sp. nov. and are not conspecific with the specimen illustrated by Cossmann (1898, pl. 8, fig. 35) as Phaneroptyxis clymene .

Endoplocus acutus sp. nov. var. (Plate 7 : figs 6, 7): Two specimens from Saal agree with E. acutus in shell shape, size (specimen illustrated in Plate 7 : figs 6, 7 is 23 mm high), and in the morphology of the plaits. However, these specimens have a subsutural spiral cord which accentuates the sutures. These specimens are considered to represent a variant of Endoplocus acutus sp. nov.

Relationships.

Endoplocus staczycii (Zeuschner, 1849) has a stouter shell, more strongly convex whorls, deeper sutures, and the last whorl is higher in relation to spire height. Endoplocus staczycii sensu Hägele (1997) shows the same differences. Endoplocus staczycii is very variable according to Peters (1855). The specimen illustrated by Peters (1855, pl. 2, fig. 6) most closely resembles Endoplocus acutus sp. nov.. However, this specimen has a stouter shell, a less slender spire, and the last whorl is higher in relation to spire height. Nerinea clymene d’Orbigny sensu Gemmellaro (1870, pl. 4, fig. 4, 5; non fig. 3) is much larger and has deep sutures that are accentuated by a narrow ramp; its shell is slenderer and has higher whorls.

Figures

Plate 7. Endoplocus acutus sp. nov. (1 - 3) Holotype, SNSB-BSPG 2021 XV 14, Saal (collection Lang); (1) apical whorls in lateral view, height 11 mm; (2) lateral view, height 29 mm; (3) aperture, height 14 mm. (4) Paratype, SNSB-BSPG 2021 XV 15, Saal (collection Keupp), lateral view, height 18.5 mm. (5) Paratype, SNSB-BSPG 2021 XV 16, Saal (collection Lang), base, width 11 mm. (6 - 7) Endoplocus acutus sp. nov. var., paratype, SNSB-BSPG 2021 XV 17, Saal (collection Lang); (6) l ateral view, height 23 mm; (7) last whorl, height 10 mm.