Kornia sphaeroidalis ( Vöhringer, 1960 ) Korn & Weyer, 2023

Korn, Dieter & Weyer, Dieter, 2023, The ammonoids from the Gattendorfia Limestone of Oberrödinghausen (Early Carboniferous; Rhenish Mountains, Germany), European Journal of Taxonomy 882, pp. 1-230 : 38-39

Kornia sphaeroidalis ( Vöhringer, 1960) comb. nov.

Fig. 24 ; Table 14

Imitoceras sphaeroidale Vöhringer, 1960: 143 , pl. 2 fig. 7.

Acutimitoceras sphaeroidale – Korn 1994: 49, text-figs 49e, 55c.

Acutimitoceras (Stockumites) sphaeroidale – Becker 1996: 36.

non Acutimitoceras sphaeroidale – Vöhringer 1960: 143, text-fig. 21. — Korn 1992b: 17, pl. 2 figs 30– 31; 1994: text-figs 50f, 51b, 55d. — Schönlaub et al. 1992: pl. 5 figs 30–31.

Diagnosis

Species of Kornia with a thickly pachyconic, involute conch (ww/dm ~0.80; uw/dm ~0.05) at 24 mm conch diameter. Ornament with widely spaced growth lines with convex course and a shallow ventral sinus.

Material examined

Holotype

GERMANY • Rhenish Mountains, Oberrödinghausen , railway cutting; Hangenberg Limestone , bed 5; Vöhringer Coll.; illustrated by Vöhringer (1960: pl. 2 fig. 7) and Korn (1994: text-fig. 49e); re-illustrated here in Fig. 24 ; GPIT-PV- 63865.

Additional material

GERMANY • 1 specimen; Rhenish Mountains, Oberrödinghausen , railway cutting; Hangenberg Limestone , bed 5a1; Weyer 1993–1994 Coll.; MB.C. 31068 .

Description

Holotype GPIT-PV-63865 ( Fig. 24A ) is a thickly pachyconic specimen with 24 mm dm (ww/dm = 0.82). It has a slightly opened umbilicus (uw/dm = 0.06) and a low coiling rate (WER = 1.67). The specimen bears small shell remnants that possess widely spaced, lamellar growth lines; these extend in a low and wide arc across the flanks and form a broad and shallow ventral sinus. Parallel to this extend faint inner shell thickenings ( Fig. 24B ).

Specimen MB.C.31068 is a rather well-preserved specimen with 13 mm conch diameter ( Fig. 24C ). It is globular and subinvolute (ww/dm = 0.91; uw/dm = 0.19) with a low coiling rate (WER = 1.56). The whorl profile is C-shaped with rounded umbilical margin and steep, flattened umbilical wall. The shell bears lamellar growth lines directed slightly backwardly from the umbilical margin and forming a shallow, very broad sinus on the venter. There is one shell constriction that extends parallel to the growth lines.

Remarks

Vöhringer (1960) united two species under the name “ Imitoceras sphaeroidale ”. Holotype GPIT- PV-63865 is a nearly globular specimen with 24 mm dm (ww/dm = 0.82), but the illustrated cross section GPIT-PV-63927 (ww/dm = 0.69 at 15 mm dm) and the smaller specimen GPIT-PV-63932 belong to a much more slender form. This is newly described here as Hasselbachia erronea sp. nov. Unfortunately, the morphology of the inner whorls is not known.

Figures

Fig. 24. Kornia sphaeroidalis (Vöhringer, 1960) from the Oberrödinghausen railway cutting.A. Holotype GPIT-PV-63865 (Vöhringer Coll.) from bed 5. B. Constriction course of holotype GPIT-PV-63865 from bed 5, at dm =22.0 mm, ww =19.4 mm, wh =12.0 mm. C. Paratype MB.C.31068 (Weyer 1993–1994 Coll.) from bed 5a1. Scale bar units= 1 mm.