Eocanites spiratissimus (Schindewolf, 1926)

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 : 203-204

Eocanites spiratissimus (Schindewolf, 1926)

Fig. 123B–F ; Tables 118–119

Protocanites spiratissimus Schindewolf, 1926: 105 .

Protocanites spiratissimus – Vöhringer 1960: 175, pl. 6 fig. 6, text-figs 45, 51.

Protocanites (Eocanites) spiratissimus – Weyer 1965: 458.

Eocanites spiratissimus – Korn 1994: 83, text-figs 73h.

Diagnosis

Species of the genus Eocanites with a conch reaching 25 mm diameter. Conch at 12 mm dm very evolute (uw/dm ~0.60) with weakly depressed whorl profile (ww/wh ~1.10) and broadly rounded venter. Ornament with very fine, rursiradiate, concavo-convex growth lines with moderately deep ventral sinus. Without ribs.

Material examined

Neotype

GERMANY • Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3c ; Vöhringer Coll.; illustrated by Vöhringer (1960: pl. 6 fig. 3) and Korn (1994: text-fig. 73h); re-illustrated here in Fig. 123B ; GPIT-PV- 64007 .

Additional material

GERMANY • 2 specimens; Rhenish Mountains , Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3c ; Vöhringer Coll.; GPIT-PV- 64012 , GPIT-PV- 64010 .

Description

Neotype GPIT-PV-64007 is a specimen with only 13 mm diameter and is largely embedded in a small limestone block ( Fig. 123B ). The dimensions can only be partially estimated, but it is clear that the conch is very evolute (uw/dm ~0.60 and that the whorl profile is almost circular. The shell appears to be smooth and bears very fine, rursiradiate growth lines.

The sectioned specimen GPIT-PV-64012 allows the study of conch geometry up to 10 mm diameter ( Fig. 123C ). The umbilicus is extremely wide between 3 and 10 mm conch diameter (uw/dm exceeds the value of 0.60) and the whorl profile decreases continuously from uw/wh ~1.40 to ~1.25.

Remarks

A type specimen was not selected when Schindewolf (1926b) described the species Eocanites spiratissimus ; obviously no later author has determined a lectotype. In his monograph, Vöhringer (1960) did not give any information on a type of the species either. For this reason, a neotype from the Vöhringer Collection from the type locality is proposed here. Eocanites spiratissimus differs from the other species of Eocanites in the very wide umbilicus at 10 mm conch diameter. The uw/dm ratio exceeds, at 10 mm conch diameter, a value of 0.60 in E. spiratissimus , but usually less than 0.55 in the other species.

Figures

Fig. 123. Eocanites from the Oberrödinghausen railway cutting, all Vöhringer Coll. A. Eocanites tener (Vöhringer, 1960), holotype GPIT-PV-64006 from bed 3c B. Eocanites spiratissimus (Schindewolf, 1926), neotype GPIT-PV-64007 from bed 3c. C. Eocanites spiratissimus (Schindewolf, 1926), cross section of specimen GPIT-PV-64012 from bed 3c. D–F. Eocanites spiratissimus (Schindewolf, 1926), 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.