Gattendorfia rhenana, 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 : 118-120

Gattendorfia rhenana sp. nov.

urn:lsid:zoobank.org:act:6E306806-364B-4DCE-8CA2-AFC203EC54E9

Figs 8A , 68–69 ; Tables 66–67

Gattendorfia subinvoluta – Schindewolf 1952: 295 fig. 15. — Vöhringer 1960: 151, pl. 5 fig. 5, text-figs 26, 35. — Korn 1994: 71, text-figs 64b–c, 65a, 66a, 67c, 68c; 2006: text-fig. 3j. — Luppold et al. 1994: text-fig. 15b. — Korn & Feist 2007: 107, text-fig. 6e, g. — Korn & Weyer 2003: 100, pl. 2 figs 10–11, text-fig. 14g. — Kullmann 2009: text-fig. 3.1. — Korn & Klug 2015: text-fig. 12.6.1. — Becker et al. 2021: text-fig. 3l–m.

Diagnosis

Species of Gattendorfia with a conch reaching 70 mm diameter. Conch at 7 mm dm thickly discoidal, evolute (ww/dm ~0.45; uw/dm ~0.55); at 15 mm dm thickly discoidal, evolute (ww/dm ~0.55; uw/dm ~0.50); at 40 mm dm thickly discoidal, subevolute (ww/dm ~0.55; uw/dm ~0.40). Whorl profile in the juvenile stage trapezoidal, at 40 mm dm moderately depressed (ww/wh ~1.60); coiling rate moderately high (WER ~1.90). Venter broadly rounded throughout ontogeny, umbilical margin narrowly rounded in the adult stage. Growth lines fine, wide-standing, with convex course. Weak constrictions on the shell surface and prominent internal shell thickenings. Suture line with narrowly lanceolate external lobe and broadly lanceolate adventive lobe.

Etymology

Named after the occurrence of the species in the Rhenish Mountains.

Material examined

Holotype

GERMANY • Rhenish Mountains, Oberrödinghausen , railway cutting; Hangenberg Limestone , bed 5; Vöhringer Coll .; illustrated by Vöhringer (1960: pl. 5 fig. 5a) and Korn (1994: text-fig. 66a); re-illustrated here in Fig. 68 ; GPIT-PV-63940.

Paratypes

GERMANY • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 5; Vöhringer Coll.; GPIT-PV-63939, GPIT-PV-63946 • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 4; Vöhringer Coll.; MB.C.31147.1–2 • 1 specimen; Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3e ; Weyer 1993–1994 Coll.; MB.C.31148 • 2 specimens; Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 6b ; Weyer 1993–1994 Coll.; MB.C.31149.1–2 • 1 specimen; Rhenish Mountains, Hasselbachtal ; Hangenberg Limestone , bed 71 ; Weyer 1993–1994 Coll.; MB.C.5244.1 • 1 specimen; Rhenish Mountains, Hasselbachtal ; Hangenberg Limestone , bed 80 ; Weyer 1993–1994 Coll.; MB.C.5247.1.

Description

Holotype GPIT-PV-63940 is a moderately well-preserved specimen with 56 mm conch diameter; it is partly covered by shell remains ( Fig. 68 ). It is thickly discoidal with a crescent-shaped, depressed whorl profile with a rounded umbilical margin and convex flanks continuing into the broadly arched venter. The specimen possesses fine growth lines and faint constrictions, which begin at the umbilical margin, from where they curve back to form a broad, shallow sinus on the venter. They are spaced at intervals of approximately 90 degrees and follow the course of the growth lines ( Fig. 69C ).

The sectioned paratype GPIT-PV-63946 allows the study of conch ontogeny in the growth interval between 5 and 28 mm diameter ( Fig. 69A ). In this growth interval, the conch becomes somewhat stouter (ww/dm increases from ~0.40 to ~0.60), while the umbilicus becomes narrower (uw/dm decreases from ~0.55 to ~0.40). The whorl profile changes from rounded trapezoidal to broad oval, but the last half whorl then shows a greater increase in whorl height. This is also expressed in the coiling rate (WER increases to ~1.90). The suture line has a lanceolate, weakly pouched external lobe, an evenly rounded, symmetrical ventrolateral saddle and a lanceolate lateral lobe ( Fig. 69B ).

Remarks

Specimens of the new species were usually attributed to Gattendorfia subinvoluta ( Vöhringer 1960; Korn 1994). However, G. subinvoluta has a much more slender conch (ww/dm ~0.42 at 62 mm dm) than G. rhenana sp. nov., where the ww/dm ratio is ~0.56 at 56 mm dm. Such a difference can hardly be explained by intraspecific variation. However, both species are easier to distinguish by the shell constrictions developed in G. rhenana , which are absent in G. subinvoluta . Furthermore, G. subinvoluta has very coarse growth lines, which are fine in G. rhenana . Such differences in G. subinvoluta were explained by Becker with the “biogeographic separation through a narrow oceanic system”. Gattendorfia rhenana differs from G. schmidti sp. nov. in the convex course of the growth lines and shell constrictions (concavo-convex in G. schmidti ) and all other species with discoidal conch in the narrower umbilicus of the adult stage and the stouter conch.

Figures

Fig. 8. Early Tournaisian representative ammonoids of the family Gattendorfiidae from the Hasselbachtal section, all Weyer 1993–1994 Coll. A. Gattendorfia rhenana sp. nov., paratype MB.C.5244.1 from bed 71. (Illustrated by Korn & Weyer 2003: pl. 2 figs 10–11, as Gattendorfia subinvoluta.) B. Weyerella molaris (Vöhringer, 1960), specimen MB.C.5240.8 from bed 57. C. Weyerella reticulum (Vöhringer, 1960), specimen MB.C.5242.1 from bed 62. D. Hasselbachia multisulcata (Vöhringer, 1960), specimen MB.C.5240.1 from bed 57. E. Hasselbachia gracilis (Vöhringer, 1960), specimen MB.C.5240.5 from bed 57. F. Pseudarietites westfalicus Schmidt, 1924, specimen MB.C.5236.1 from bed 49. Scale bar units =1 mm.

Fig. 68. Gattendorfia rhenana sp. nov.; holotype GPIT-PV-63940 (Vöhringer Coll.) from the Oberrödinghausen railway cutting, bed 5. Scale bar units =1 mm.

Fig. 69. Gattendorfia rhenana sp. nov. from the Oberrödinghausen railway cutting. A. Cross section of paratype GPIT-PV-63946 from bed 5. B. Suture line of paratype GPIT-PV-63946 from bed 5, at ww =11.5 mm, wh =6.0 mm. C. Growth line course of holotype GPIT-PV-63940 from bed 5, at ww ~ 32.0 mm, wh=18.0 mm. D–F. 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.