Eocanites ruani Bartzsch, Korn & Weyer, 2003

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 : 194-196

Eocanites ruani Bartzsch, Korn & Weyer, 2003

Figs 117–118

Eocanites ruani Bartzsch, Korn & Weyer, 2003: 8 , text-figs 1–2.

Gattendorfia nodosa Schmidt, 1925: 536 , pl. 19 fig. 10, pl. 23 fig. 3.

Protocanites nodosus – Vöhringer 1960: 169, pl. 6 fig. 1b, text-fig. 44a.

Eocanites nodosus – Korn & Feist 2007: 108, text-fig. 6f.

non Eocanites ruani Becker & Weyer 2004: 8 , text-fig. 17.

Diagnosis

Species of the genus Eocanites with a conch reaching 50 mm diameter. Conch at 12 mm dm evolute (uw/dm ~0.50) with weakly depressed whorl profile (ww/wh ~1.05) and broadly rounded venter; conch at 30 mm dm evolute (uw/dm ~0.50) with weakly compressed whorl profile (ww/wh ~0.95) and flat or weakly concave venter. Ornament with moderately coarse, strongly rursiradiate, biconvex growth lines with deep ventral sinus. With low, rounded crescent-shaped ventrolateral ribs and nodes.

Material examined

Holotype

GERMANY • Thuringian Mountains, Saalfeld, Pfaffenberg SW quarry; Pfaffenberg Member of the Gleitsch Formation, bed 4; Bartzsch & Weyer 1974 Coll.; illustrated by Bartzsch et al. (2003: text-fig. 1.1) and Korn (2006: text-fig. 4i); MB.C.5360.1.

Paratypes

GERMANY • 10 specimens; Thuringian Mountains , Saalfeld, Pfaffenberg SW quarry; Pfaffenberg Member of the Gleitsch Formation, bed 4; Bartzsch & Weyer 1967–1976 Coll.; MB.C.5360.2–

MB.C.5360.9, MB.C.5361, MB.C.5362.1 • 1 specimen; Thuringian Mountains, Saalfeld, Pfaffenberg SW quarry; Pfaffenberg Member of the Gleitsch Formation, bed 4; Riedel Coll.; MB.C.5362.2.

Additional material

GERMANY • 1 specimen; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 4; Vöhringer Coll.; GPIT-PV-63970 • 1 specimen; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 5; Vöhringer Coll.; GPIT-PV-64001 • 3 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 4a; Weyer 1993–1994 Coll.; MB.C.31228.1–3 • 1 specimen; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 5a1; Weyer 1993–1994 Coll.; MB.C.31229 • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 5a2; Weyer 1993–1994 Coll.; MB.C.31230.1–2 • 1 specimen; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 5b; Weyer 1993–1994 Coll.; MB.C.31231 • 1 specimen; Rhenish Mountains , Drewer; Hangenberg Limestone; Schmidt Coll.; GZG.INV.1690 .

Description

Specimen MB.C.31229 is a small fragment, but it clearly shows the characteristic features of the species ( Fig. 117B ). At 9 mm whorl height, the profile has almost equal width and height, but the flanks converge to the flattened, slightly concave venter. The specimen shows crescent-shaped ribs on the outer flank; these ribs form blunt nodes on the ventrolateral shoulder.

The transition to the adult stage can also be followed in the sectioned specimen GPIT-PV-63970; the almost circular juvenile whorl profile has developed a concave venter at 8 mm whorl height ( Fig. 118A ). The ontogenetic trajectories of the cardinal conch parameters are rather simple, at least to a conch diameter of 9 mm ( Fig. 118 C-E).

The fragment of the larger specimen GPIT-PV-64001 represents the adult stage with flat venter and ribs on the flank, which turn into short nodes near the ventrolateral shoulder ( Fig. 117A ).

Remarks

Specimens of Eocanites ruani were considered by Schmidt (1925), Vöhringer (1960) and Korn (1994) as adult stages of E. nodosus . However, E. nodosus has a much finer ornament with coarse growth lines formed on the entire flank and venter; furthermore, ribs, nodes and a concave venter are not known from E. nodosus .

Eocanites ruani can be easily distinguished from almost all other Central European species of the genus by the concave venter and the characteristic crescent-shaped ribs on the outer half of the flank. Eocanites ruani is so far apparently the only representative of the genus from the lower part of the Gattendorfia stage.

Of the species of Eocanites described from Guizhou, E. holcoventrus and E. robustus have a concave venter, but both species have an almost square-shaped whorl profile. Furthermore, E. holcoventrus has no ribs and E. robustus has sigmoidally curved ribs on the flank.

Figures

Fig. 117. Eocanites ruani (Bartzsch, Korn & Weyer, 2003) from the Oberrödinghausen railway cutting. A. Specimen GPIT-PV-64001 (Vöhringer Coll.) from bed 5. B. Specimen MB.C.31229 (Weyer 1993– 1994 Coll.) from bed 5a1. C. Reproduction of the figure of “Gattendorfia nodosa” of Schmidt (1925: pl. 23 fig. 3). Scale bar units=1 mm.

Fig. 118. Eocanites ruani (Bartzsch, Korn & Weyer, 2003) from the Oberrödinghausen railway cutting. A. Cross section of specimen GPIT-PV-63970 (Vöhringer Coll.) from bed 4 (after Vöhringer 1960). B. Growth line course of specimen MB.C.31229 (Weyer 1993–1994 Coll.) from bed 5a1, at ww =9.7 mm, wh =9.3 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.