Kornia fibula, 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 : 39-41

Kornia fibula sp. nov.

urn:lsid:zoobank.org:act:D2D2D504-131B-4342-9CEC-4C8E29E433C1

Figs 25–26 ; Tables 15–16

Paragattendorfia n. sp. I Korn & Weyer, 2003: 95, pl. 2 figs 20–21.

Paragattendorfia cf. sphaeroides Becker et al., 2021 : text fig. 3n–o.

Gattendorfia cf. crassa – Becker 1997: 34, pl. 1 fig. 10.

Diagnosis

Species of Kornia with globular, moderately involute conch (ww/dm ~0.95; uw/dm ~0.15) at 12 mm conch diameter. Growth lines with very deep and wide external sinus.

Etymology

From the Latin ‘ fibula ’ = ‘clasp’, a connotation of the name of the type locality at Oese.

Material examined

Holotype

GERMANY • Rhenish Mountains , Oese , old quarry; Hangenberg Limestone, bed 28; Weyer & Korn 2000 Coll.; illustrated by Korn & Weyer (2003: pl. 2 figs 20–21); re-illustrated here in Fig. 25B ; MB.C.5260.3 .

Paratypes

GERMANY • 2 specimens; Rhenish Mountains, Oberrödinghausen , railway cutting; Hangenberg Limestone , bed 2a; Weyer 1993–1994 Coll.; MB.C.31069.1–2 • 1 specimen; Rhenish Mountains, Oberrödinghausen , railway cutting; Hangenberg Limestone , bed 3d1b; Weyer 1993–1994 Coll.; MB.C.31070 • 2 specimens; Rhenish Mountains , Oberrödinghausen , railway cutting; Hangenberg Limestone , bed 3d2; Weyer 1993–1994 Coll.; MB.C.31071.1–2 • 3 specimens; Rhenish Mountains , Oese , old quarry; Hangenberg Limestone, bed 22; Weyer & Korn 2000 Coll.; MB.C.5262.2 , MB.C.5262.4 , MB.C.5262.5 • 1 specimen; Rhenish Mountains , Letmathe, between Schälk and Grürmannsheide; Hangenberg Limestone; Denckmann 1901 Coll.; MB.C.1215 .

Description

Holotype MB.C.5260.3 ( Fig. 25B ), measuring 11.4 mm diameter, has an almost ball-shaped conch with a small umbilicus and a low aperture (ww/dm = 0.94; uw/dm = 0.15; WER = 1.46) and a C-shaped whorl profile. The ornament possesses lamellar growth lines that are strongly rursiradiate in their direction. They form a low dorsolateral projection and already on the inner flank turn back to extend with a deep and wide sinus across the outer flanks and the venter ( Fig. 26B ).

The larger paratype MB.C.31069.2 ( Fig. 25A ) with 16 mm conch diameter displays a similar growth line course, but with less strong backward turn. It has a globular, involute conch (ww/dm = 0.87; uw/ dm = 0.11).

The sectioned paratype MB.C.31069.1 allows the study of conch geometry between 4.7 and 19.2 mm diameter ( Fig. 26A ). During this growth interval, the whorl profile maintains a similar shape. The venter is broad and merges continuously into the convex flanks; the umbilical margin is rounded. The growth trajectories show an almost isometric ontogeny in this growth interval ( Fig. 26C–D ).

Remarks

Kornia fibula sp. nov. differs from K. acia sp. nov. in the ball-shaped juvenile conch (spindle-shaped in K. acia ) and wider umbilicus at 10 mm conch diameter (uw/dm = 0.15 in K. fibula but only 0.10 in K. acia ). The superficially similar Globimitoceras globiforme differs in the narrower umbilicus (uw/ dm ~ 0.15 in Kornia fibula but only 0.08 in G. globiforme at 10–15 mm dm).

Figures

Fig. 25. Kornia fibula sp. nov. A. Paratype MB.C.31069.2 (Weyer 1993–1994 Coll.) from Oberrödinghausen, bed 2a. B. Holotype MB.C.5260.3 (Weyer 1993–1994 Coll.) from Oese, bed 28. Scale bar units =1 mm.

Fig. 26. Kornia fibula sp. nov. A. Cross section of paratype MB.C.31069.1 (Weyer 1993–1994 Coll.) from Oberrödinghausen, bed 2a. B. Growth line course of holotype MB.C.5260.3 (Weyer 1993–1994 Coll.) from Oese, bed 28, at dm=9.8 mm, ww =9.9 mm, wh= 4.8 mm. C–E. Ontogenetic development of the conch width index (ww/dm), umbilical width index (uw/dm), whorl width index (ww/wh) and whorl expansion rate (WER) of selected specimens. Scale bar units=1 mm.