Eocanites delicatus, 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 : 206-208

Eocanites delicatus sp. nov.

urn:lsid:zoobank.org:act:84F708EA-F37B-4DF4-8503-B777178537CA

Figs 125–126 ; Tables 121–122

Protocanites Lyoni – Schmidt 1924: 153, pl. 8 figs 14–18. — Schmidt, 1925: 537, pl. 19 fig. 11.

Protocanites supradevonicus supradevonicus – Vöhringer 1960: 171, pl. 6 fig. 2, text-figs 46b, 48.

Eocanites supradevonicus – Korn 1994: 80, text-figs 66m, 73e, 74c, 75a; 2006: text-fig. 4j. — Kullmann 2000: text-fig. 4m. — Sprey 2002: 53, text-fig. 18g. — Furnish et al. 2009: text-fig. 117.2.

Diagnosis

Species of the genus Eocanites with a conch reaching 60 mm diameter. Conch at 12 mm dm evolute (uw/dm ~0.55) with weakly depressed whorl profile (ww/wh ~1.10) and broadly rounded venter; conch at 30 mm dm evolute (uw/dm ~0.50) with nearly circular whorl profile (ww/wh ~1.00) and broadly rounded venter. Ornament with fine, rursiradiate, concavo-convex growth lines with moderately deep ventral sinus. With low, rounded folds on the flank. Suture line with weakly pouched external lobe and lanceolate, weakly pouched adventive lobe.

Etymology

From the Latin ‘ delicatus ’, referring to the delicate shell ornament.

Material examined

Holotype

GERMANY • Rhenish Mountains, Oberrödinghausen , railway cutting; Hangenberg Limestone , bed 1; Vöhringer Coll.; illustrated by Vöhringer (1960: pl. 6 fig. 2), Korn (1994: text-fig. 73e) and Korn (2006: text-fig. 4j); re-illustrated here in Fig. 125A .; GPIT-PV-63997.

Paratypes

GERMANY • 1 specimen; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone,bed1; Vöhringer Coll.;GPIT-PV-64008 • 2specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 2; Vöhringer Coll.; GPIT-PV-63981, GPIT-PV-63999 • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, loose material; Korn 1977 Coll.; MB.C.31247.1–2 • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, loose material; Korn 1990 Coll.; MB.C.31248.1–2 • 1 specimen; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 2b; Korn 1991 Coll.; MB.C.31249 • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 1; Weyer 1993–1994 Coll.; MB.C.31250.1–2 • 10 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 2a; Weyer 1993–1994 Coll.; MB.C.31251.1–10 • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 2b; Weyer 1993–1994 Coll.; MB.C.31252.1–2 .

Description

Holotype GPIT-PV-63997 is a well-preserved specimen with 42 mm conch diameter embedded in rock matrix ( Fig. 125A ). The conch is extremely discoidal with a wide umbilicus (ww/dm ~0.25; uw/dm ~0.50) and a compressed oval whorl profile (ww/wh ~0.85); the coiling rate is low (WER ~1.70). The shell bears fine, regularly spaced growth lines that are directed backwards on the flank. A very weak radial folding is also visible on the flank.

Paratype MB.C.31247.1 is a specimen with 31 mm diameter ( Fig. 125B ); it is thinly discoidal and evolute with a nearly circular whorl profile (ww/dm ~0.28; uw/dm ~0.50; ww/wh ~0.96). The ornament consists of fine growth lines running backwardly directed across the flanks and form a rounded ventral sinus.

Eocanites delicatus sp. nov. has, like most of the other early prolecanitid ammonoids, a rather simple conch ontogeny with nearly monophasic trajectories of the cardinal conch parameters. As seen in specimens GPIT-PV-64008 ( Fig. 126A ) and GPIT-PV-63981 ( Fig. 126B ), the uw/dm trajectory decreases from about 0.65 at 1.2 mm diameter to 0.28 at 12 mm diameter. The uw/dm trajectory shows an initial increase to 0.57 at 3 mm diameter and then stays at this value. The whorl expansion rate fluctuates between 1.60 and 1.70 in the growth interval between 2 and 12 mm diameter ( Fig. 126E–G ).

Remarks

The holotype that was illustrated by Vöhringer (1960) under the name Eocanites supradevonicus has a much weaker ornament than the specimen of the poor illustration given by Schindewolf (1926b) and is thus not included in that species.

Eocanites delicatus sp. nov. can be distinguished from E. supradevonicus by several characteristics. Firstly, the conch of E. delicatus is slightly less widely umbilicate (uw/dm ~ 0.50 in contrast to E. supradevonicus with a value of ~0.55) and secondly, E. delicatus shows only very weak folds on the flank, which are developed much stronger in E. supradevonicus . Eocanites delicatus differs from the similar species E. brevis in the shape of the whorl profile, which in E. delicatus is still almost circular at 35 mm conch diameter, whereas in E. brevis it is already compressed at 10 mm conch diameter (ww/ wh ~0.90). Eocanites planus and E. tener also differ from E. delicatus in this respect.

Figures

Fig. 125. Eocanites delicatus sp. nov. from the Oberrödinghausen railway cutting. A. Holotype GPIT- PV-63997 (Vöhringer Coll.) from bed 1.B. Paratype MB.C.31247.1 (Korn 1977 Coll.) from an unknown bed. Scale bar units = 1 mm.

Fig. 126. Eocanites delicatus sp. nov. from the Oberrödinghausen railway cutting. A. Cross section of paratype GPIT-PV-64008 (Vöhringer Coll.) from bed 2. B. Cross section of paratype GPIT-PV-63981 (Vöhringer Coll.) from bed 2. C. Suture line of paratype GPIT-PV-63999 (Vöhringer Coll.) from bed 2, at ww =6.8 mm, wh =6.5 mm. D. Growth line course of paratype GPIT-PV-64008 (Vöhringer Coll.) from bed 1, at dm =43.0 mm, ww =11.0 mm, wh=13.5 mm. E–G. 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.