The ammonoids from the Gattendorfia Limestone of Oberrödinghausen (Early Carboniferous; Rhenish Mountains, Germany) Author Korn, Dieter 286CA4F3-7EBC-4AEF-A66A-B2508D001367 Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, 10115 Berlin, Germany. dieter.korn@mfn.berlin Author Weyer, Dieter A09A1738-C70E-4F22-A069-8B7DB4A1753D Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, 10115 Berlin, Germany. dieter.weyer@t-online.de text European Journal of Taxonomy 2023 2023-07-19 882 1 230 http://dx.doi.org/10.5852/ejt.2023.882.2177 journal article 58033 10.5852/ejt.2023.882.2177 57d1d191-2bf5-4229-a0f5-9ab472a114a6 2118-9773 8177581 67C909E4-C700-4F8D-B8CE-5FD9B2C5D549 Stockumites undulatus ( Vöhringer, 1960 ) comb. nov. Figs 37–38 ; Tables 32–33 Imitoceras undulatum Vöhringer, 1960: 133 , pl. 3 fig. 6, text-fig. 13. Acutimitoceras undulatum Korn 1994: 52 , text-figs 49h–i, 50l, 52c, 55e–f. — Korn et al . 1994 : text-fig. 20a. Diagnosis Species of Stockumites with a conch reaching 40 mm diameter. Conch at 5 mm dm thinly pachyconic, subinvolute (ww/dm ~0.70; uw/dm ~0.25); at 12 mm dm thinly pachyconic, subinvolute (ww/dm ~0.65; uw/dm ~0.05); at 20 mm dm thickly discoidal, involute (ww/dm ~0.55; uw/dm ~0.02). Whorl profile at 20 mm dm weakly compressed (ww/wh ~0.95); coiling rate moderately high (WER ~1.90). Venter broadly rounded, umbilical margin broadly rounded. Growth lines lamellar, wide-standing, with biconvex course. Without constrictions on the shell surface; without internal shell thickenings. Suture line with V-shaped external lobe and V-shaped adventive lobe. Material examined Holotype GERMANYRhenish Mountains , Oberrödinghausen , railway cutting; Hangenberg Limestone , bed 5; Vöhringer Coll .; illustrated by Vöhringer (1960 : pl. 3 fig. 6) and Korn (1994: text-fig. 49i ); re-illustrated here in Fig. 37A ; GPIT-PV-63877. Paratypes GERMANY1 specimen ; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone,bed5;Vöhringer Coll.;GPIT-PV-64022• 2specimens ;Rhenish Mountains,Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 6; Vöhringer Coll.; GPIT-PV-63879, GPIT-PV-63881. Additional material GERMANY1 specimen ; Rhenish Mountains , Oberrödinghausen , railway cutting; Hangenberg Limestone , bed 6; Vöhringer Coll.; MB.C.31089 1 specimen ; Rhenish Mountains , Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 5c; Weyer 1993–1994 Coll.; MB.C.31090 1 specimen ; Rhenish Mountains , Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 6a; Weyer 1993– 1994 Coll.; MB.C.31091 1 specimen ; Rhenish Mountains , Oese , old quarry ; bed interval III ; Paproth Coll.; MB.C.5271. Fig. 37. Stockumites undulatus ( Vöhringer, 1960 ) from the Oberrödinghausen railway cutting. A . Holotype GPIT-PV-63877 (Vöhringer Coll.) from bed 5. B . Paratype GPIT-PV-63879 (Vöhringer Coll.) from bed 6. Scale bar units =1 mm. Description Holotype GPIT-PV-63877 is a specimen that is largely covered with shell and has 23 mm diameter ( Fig. 37A ). It is thickly discoidal (ww/dm = 0.52) with a closed umbilicus. The conch is widest at the rounded umbilical margin; from there the flanks converge to the continuously rounded venter. The ornament consists of lamellar growth lines with a biconvex course; the dorsolateral projection and ventrolateral projection have about the same height ( Fig. 38E ). Paratype GPIT-PV-63879 with 20.5 mm diameter is very similar to the holotype in conch parameters and ornament ( Fig. 37B ). The suture line has a lanceolate external lobe, accompanied by an asymmetrical ventrolateral saddle. The almost symmetrical adventive lobe is broadly lanceolate with outwardly curved flanks ( Fig. 38C ). Specimen MB.C.31091 shows the ornament in particularly good preservation ( Fig. 38A ). The lamellar growth lines with biconvex course form a dorsolateral projection on the inner third of the flank, a shallow lateral sinus on the outer third of the flank and a ventrolateral projection on the ventrolateral shoulder. Fig. 38. Stockumites undulatus ( Vöhringer, 1960 ) from the Oberrödinghausen railway cutting. A . Specimen MB.C.31091 (Weyer 1993–1994 Coll.) from bed 6a. B . Cross section of paratype GPIT- PV-63881 (Vöhringer Coll.) from bed 6. C . Suture line of paratype GPIT-PV-63879 (Vöhringer Coll.) from bed 6, at ww=8.5 mm, wh =7.6 mm. D . Growth line course of paratype GPIT-PV-63881 (Vöhringer Coll.) from bed 5, at dm =9.5 mm, ww =6.0 mm, wh =5.5 mm. E . Growth line course of holotype GPIT- PV-63877 (Vöhringer Coll.) from bed 5, at dm =16.3 mm, ww =9.2 mm, wh =9.0 mm. F–H . 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. Table 32. Conch measurements, ratios and rates of Stockumites undulatus ( Vöhringer, 1960 ) from Oberrödinghausen.
specimen dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR
GPIT-PV-63877 22.8 11.9 13.7 0.4 6.5 0.52 0.87 0.02 1.96 0.53
MB.C.31091 21.7 11.0 11.5 0.6 5.8 0.51 0.96 0.03 1.87 0.49
GPIT-PV-63879 20.4 11.3 11.4 0.5 5.7 0.55 0.99 0.02 1.93 0.50
GPIT-PV-63881 8.9 5.9 4.9 0.6 2.3 0.67 1.21 0.07 1.83 0.52
Table 33. Conch ontogeny of Stockumites undulatus ( Vöhringer, 1960 ) from Oberrödinghausen.
dm conch shape whorl cross section shape whorl expansion
2 mm thinly pachyconic; subevolute (ww/dm ~0.70; uw/dm ~0.35) moderately depressed; strongly embracing (ww/wh ~1.90; IZR ~0.35) low (WER ~1.70)
4 mm thinly pachyconic; subinvolute (ww/dm ~0.70; uw/dm ~0.25) weakly depressed; very strongly embracing (ww/wh ~1.50; IZR ~0.45) moderate (WER ~1.80)
12 mm thinly pachyconic; involute (ww/dm ~0.65; uw/dm ~0.05) weakly depressed; very strongly embracing (ww/wh ~1.10; IZR ~0.55) moderate (WER ~1.80)
20 mm thickly discoidal; involute (ww/dm ~0.55; uw/dm ~0.02) weakly compressed; very strongly embracing (ww/wh ~0.95; IZR ~0.55) moderate (WER ~1.90)
Remarks Stockumites undulatus is an easily recognisable species because it is clearly distinguished from all other species of the genus by the characteristic, lamellar growth lines with a distinctive biconvex course.