Hasselbachia multisulcata ( Vöhringer, 1960 )

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 : 162-165

Hasselbachia multisulcata ( Vöhringer, 1960)

Figs 8D , 97 , 98A–D , 99 ; Tables 95–96

Imitoceras multisulcatum Vöhringer, 1960: 141 , pl. 4 fig. 5, text-fig. 19.

Imitoceras multisulcatum – Weyer 1976: 841, text-fig. 4.

Acutimitoceras multisulcatum – Korn 1994: 47, text-figs 49g, l, 50j–k, 51c, 55b.

Hasselbachia multisulcata – Korn & Weyer 2003: 96, pl. 1 figs 7–8, text-fig. 14e–f. — Korn 2006: text-fig. 3e.

Acutimitoceras (Stockumites) multisulcatum – Sprey 2002: 52, pl. 4 fig. 5, text-fig. 17f.

Imitoceras (Imitoceras) multisulcatum – Ruan 1981: 80, pl. 18 figs 5–7, pl. 19 figs 1–13.

Diagnosis

Species of Hasselbachia with a globular and subevolute conch at 5 mm dm (ww/dm = 0.85–0.95; uw/ dm = 0.40–0.45) and a thinly pachyconic and subinvolute conch at 15 mm dm (ww/dm = 0.60–0.65; uw/ dm = 0.15–0.25). Whorl cross section at 15 mm dm weakly depressed (ww/wh = 1.25–1.50); coiling rate very low (WER ~1.45). Flanks strongly convergent. Shell ornament with coarse lamellar growth lines with convex course. Shell and internal mould with numerous short constrictions on the flank.

Material examined

Holotype

GERMANY • Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3e ; Vöhringer Coll.; illustrated by Vöhringer (1960: pl. 4 fig. 5), Korn (1994: text-fig. 58b) and Korn (2006: text-fig. 3e); re-illustrated here in Fig. 97B ; GPIT-PV-63911.

Paratypes

GERMANY • 1 specimen; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3d; Vöhringer Coll.; GPIT-PV-63938 • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3e; Vöhringer Coll.; GPIT-PV-63949, GPIT-PV-64017 • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 4; Vöhringer Coll.; GPIT-PV-63913, GPIT-PV-63915 .

Additional material

GERMANY • 2 specimens; Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3d1b ; Weyer 1993–1994 Coll.; MB.C.31193.1–2 • 3 specimens; Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3d2 ; Weyer 1993–1994 Coll.; MB.C.31194.1–3 • 5 specimens; Rhenish Mountains, Oberrödinghausen , railway cutting ; Hangenberg Limestone , bed 3e ; Weyer 1993–1994 Coll.; MB.C.31195.1–5 • 4 specimens; Rhenish Mountains, Hasselbachtal ; Hangenberg Limestone , bed 57; Weyer 1993–1994 Coll.; MB.C.5240.1–MB.C.5240.4.

Description

The two type specimens GPIT-PV-63911 and GPIT-PV-63913 ( Fig. 97 ) are moderately well-preserved. Therefore, several specimens from new collections are described in more detail below. Holotype GPIT- PV-63911 has a conch diameter of 15 mm and is thinly pachyconic and involute (ww/dm = 0.69; uw/ dm = 0.11). The shell shows growth lines that extend with a slightly convex curve across the flank and form a very broad, shallow ventral sinus ( Fig. 99G ).

The four rather well-preserved specimens MB.C.31195.1 (22 mm dm), MB.C.31195.2 (16.5 mm dm), MB.C.31194.1 (16 mm dm) and MB.C.31195.3 (15 mm dm) allow the study of conch shape and ornament ( Fig. 98A–D ). All of them are very similar in their conch proportions; they are thinly pachyconic (ww/ dm = 0.60–0.63) and involute (uw/dm = 0.10–0.15). All show rapid closure of the umbilicus by overlap of the last whorl, meaning that the absolute umbilical diameter is reduced. The whorl profile has a semilunate shape with little space on the lateral sides; the flanks converge rather rapidly towards the broadly rounded venter.

The shell ornament is best preserved in specimen MB.C.31195.1 ( Fig. 98A ). It shows lamellar growth lines extending convexly with a broad arch across the flanks and form a shallow sinus across the venter. Like the other two specimens, it possesses only very weak and short constrictions in the midflank area.

Vöhringer produced three cross sections but published only one of them. These three are GPIT-PV-64017 (8.5 mm dm), GPIT-PV-63938 (13 mm dm) and GPIT-PV-63949 (14.5 mm dm) ( Fig. 99A–C ). None of them has the innermost whorls preserved, but these can be seen in specimen MB.C.5240.2 from Hasselbachtal ( Fig. 99D ). The conch shape and its proportions change markedly during ontogeny with a triphasic ww/dm trajectory and a biphasic uw/dm trajectory. The coiling rate decreases in the early juvenile stage to WER = 1.60 at 2.5 mm conch diameter, then slowly decreases to 1.50 and remains stable at this value until 17 mm diameter. The whorl profile is strongly depressed in the juvenile stage up to a conch diameter of 9 mm (ww/wh higher than 2.50); up to this size, the umbilicus is opening continuously. Thereafter, the whorls begin to embrace the umbilicus, which can best be observed in the specimens from the Hasselbachtal section ( Fig. 99D–E ).

The suture line of paratype GPIT-PV-64017 has a lanceolate external lobe accompanied by a slightly asymmetrical, rounded ventrolateral saddle. The adventive lobe is V-shaped with slightly outwardly curved flanks ( Fig. 99F ).

Remarks

Hasselbachia multisulcata differs from H. gracilis by the wider conch in combination with a narrower umbilicus. The uw/dm ratio, at 17 mm conch diameter, is about 0.27 in H. gracilis , but only about 0.13 in H. multisulcata .

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. 97. Hasselbachia multisulcata (Vöhringer, 1960) from the Oberrödinghausen railway cutting, both Vöhringer Coll. A. Paratype GPIT-PV-63913 from bed 4. B. Holotype GPIT-PV-63911 from bed 3e. Scale bar units= 1 mm.

Fig. 98. Hasselbachia from the Oberrödinghausen railway cutting, all Weyer 1993–1994 Coll. A. Hasselbachia multisulcata (Vöhringer, 1960), specimen MB.C.31195.1 from bed 3e. B. Hasselbachia multisulcata (Vöhringer, 1960), specimen MB.C.31195.2 from bed 3e. C. Hasselbachia multisulcata (Vöhringer, 1960), specimen MB.C.31194.1 from bed 3d2. D. Hasselbachia multisulcata (Vöhringer, 1960), specimen MB.C.31195.3 from bed 3e. E. Hasselbachia gracilis (Vöhringer, 1960), specimen MB.C.31196.1 from bed 3d1b. Scale bar units =1 mm.

Fig. 99. Hasselbachia multisulcata (Vöhringer, 1960) from the Oberrödinghausen railway cutting (A-C, F, G) and the Hasselbachtal section (D, E; after Korn & Weyer 2003). A. Cross section of paratype GPIT-PV-63938 (Vöhringer Coll.) from bed 3e. B. Cross section of paratype GPIT-PV-63949 (Vöhringer Coll.) from bed 3d. C. Cross section of paratype GPIT-PV-64017 (Vöhringer Coll.) from bed 3e. D. Cross section of specimen MB.C.5240.2 (Weyer 1993–1994 Coll.) from bed 57. E. Cross section of specimen MB.C.5240.3 (Weyer 1993–1994 Coll.) from bed 57. F. Suture line of paratype GPIT-PV-64017 (Vöhringer Coll.) from bed 3e, at dm =8.8 mm, ww = 7.7 mm, wh =4.3 mm. G. Growth line course of holotype GPIT-PV-63911 (Vöhringer Coll.) from bed 3e, at 13.2 mm dm, 10.0 mm ww, 7.0 mm wh. H–J. 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 (holotype of Hasselbachia gracilis as grey dots). Scale bar units =1 mm.