Stockumites voehringeri, 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 : 70-75

Stockumites voehringeri sp. nov.

urn:lsid:zoobank.org:act:A4D85F08-B03D-4D33-AA18-5187E9F3E0B8

Figs 7C , 42–45 ; Tables 38–39

Imitoceras subbilobatum – Vöhringer 1960: 135, pl. 3 fig. 3.

Acutimitoceras subbilobatum – Korn 1994: 51, text-figs 44d–f, 47a, 53a–b, 58f.

Acutimitoceras (Stockumites) subbilobatum – Sprey 2002: pl. 4 fig. 2.

Acutimitoceras cf. intermedium – Korn & Weyer 2003: pl. 1 figs 1–2.

Rectimitoceras substriatum – Sprey 2002: pl. 3 fig. 2.

Diagnosis

Species of Stockumites with a conch reaching 70 mm diameter. Conch at 5 mm dm globular, subinvolute to subinvolute (ww/dm ~0.90; uw/dm ~0.20); at 15 mm dm thickly pachyconic, involute (ww/dm ~0.75; uw/dm ~0.05); at 30 mm dm thickly discoidal, involute (ww/dm = 0.50–0.60; uw/dm ~0.00). Whorl profile at 30 mm dm weakly compressed to weakly depressed (ww/wh = 0.90–1.10); coiling rate moderately high (WER = 1.80–1.95). Venter broadly rounded, umbilical margin rounded. Growth lines fine, wide-standing, with convex course. Without constrictions on the shell surface; with prominent internal shell thickenings on the outer flank and the venter. Suture line with lanceolate external lobe and V-shaped adventive lobe.

Etymology

Named after Eugen Vöhringer in appreciation of his monograph on the ammonoids of Oberrödinghausen.

Material examined

Holotype

GERMANY • Rhenish Mountains, Oberrödinghausen , railway cutting; Hangenberg Limestone , bed 3b; Vöhringer Coll.; illustrated by Vöhringer (1960: pl. 3 fig. 3a, as Imitoceras subbilobatum ), Korn (1994: text-fig. 44e, as Acutimitoceras subbilobatum ) and Sprey (2002: pl. 4 fig. 2, as Acutimitoceras (Stockumites) subbilobatum ); re-illustrated here in Fig. 42A ; GPIT-PV-63995.

Paratypes

GERMANY • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 2; Vöhringer Coll.; GPIT-PV-63888, GPIT-PV-64005 • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3b; Vöhringer Coll.; GPIT- PV-63883, GPIT-PV-63885 • 1 specimen; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3d; Vöhringer Coll.; GPIT-PV-63851 • 1 specimen; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3e; Vöhringer Coll.; GPIT-PV-63850 • 1 specimen; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 4; Vöhringer Coll.; GPIT-PV-63988 • 1 specimen; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3a; Vöhringer Coll.; MB.C.31097 • 3 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3b; Vöhringer Coll.; MB.C.31098.1– 4 • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 4; Vöhringer Coll.; MB.C.31099.1–2 • 3 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, loose material; Vöhringer Coll.; MB.C.31100.1–3 • 6 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, loose material; Korn 1977 Coll.; MB.C.31101.1–6 • 1 specimen; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, loose material; Korn 1982 Coll.; MB.C.31102 • 3 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, loose material; Korn 1990 Coll.; MB.C.31103.1–3 • 6 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3a; Korn 1991 Coll.; MB.C.31104.1–6 • 1 specimen; Rhenish Mountains , Oberrödinghausen, west of railway cutting; Hangenberg Limestone, loose material; Korn 1977 Coll.; MB.C.31105 • 3 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3a; Weyer 1993–1994 Coll.; MB.C.31106.1–3 • 7 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3b; Weyer 1993–1994 Coll.; MB.C.31107.1–7 • 5 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3c1; Weyer 1993–1994 Coll.; MB.C.31108.1–5 • 7 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3d1; Weyer 1993–1994 Coll.; MB.C.31109.1–7 • 8 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3d1b; Weyer 1993–1994 Coll.; MB.C.31110.1–8 • 3 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3d2; Weyer 1993–1994 Coll.; MB.C.31111.1–3 • 8 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3e; Weyer 1993–1994 Coll.; MB.C.31112.1–8 • 1 specimen; Rhenish Mountains , Oberrödinghausen, road cutting; Hangenberg Limestone, bed 3d; Korn & Weyer 2000 Coll.; MB.C.31113 • 1 specimen; Rhenish Mountains , Hasselbachtal; Hangenberg Limestone, bed 45; Weyer 1993–1994 Coll.; MB.C.5234.1 • 1 specimen; Rhenish Mountains , Hasselbachtal; Hangenberg Limestone, bed 46; Weyer 1993–1994 Coll.; MB.C.5235.1 • 1 specimen; Rhenish Mountains , Oese, old quarry; bed interval V; Paproth Coll.; MB.C.5274 .

Description

Holotype GPIT-PV-63995 is an almost complete, rather well preserved specimen with a diameter of 56 mm ( Fig. 42A ). It is thickly discoidal (ww/dm = 0.51) with a completely closed umbilicus. The whorl profile is widest in the immediate vicinity of the rounded umbilical margin, from where the flanks converge strongly towards the comparatively narrowly rounded venter. The whorl expansion rate almost reaches the value of 2.00. Areas of the specimen are covered with shell remains; these show fine growth lines, which extend almost straight across the flank and form a sinus on the venter. The internal mould bears several wide and rather deep constrictions, which are produced by prominent radial internal shell thickenings. They are largely parallel to the growth lines ( Fig. 44E ).

The suture lines of the two paratypes MB.C.31111.3 ( Fig. 44B ) and GPIT-PV-63885 ( Fig. 44C ) closely resemble each other. Both show a lanceolate external lobe and a V-shaped adventive lobe.

Two complete cross sections are available for study; paratype MB.C.31111.2 (24 mm dm; Fig. 44A ) and paratype MB.C.31099.1 (53 mm dm; Fig. 45A ) show almost identical section images in juvenile and middle growth stages. Both show the transformation of the short widely umbilicate initial stage (up to 2.5 mm dm) to the stout late juvenile stage between 4 and 7 mm conch diameter, where the conch is almost spherical (ww/dm = 0.90). Thereafter, there is a rapid increase in whorl height; at the same time, the flanks become significantly more convergent.

The intraspecific variation is rather low ( Fig. 44F–H ) and seems to increase in the middle and adult stages. However, this effect in the diagrams is possibly caused by the large number of specimens from this size class, while only two very similar specimens allow the study of juvenile morphology.

Remarks

Specimens of the new species Stockumites voehringeri sp. nov. were included in S. subbilobatus by ( Vöhringer 1960) and (Korn 1994). The two species differ in the shape of the conch and the ornament of the shell. Stockumites voehringeri has convergent flanks, but they are almost parallel or only slightly convergent in S. subbilobatus . In addition, S. voehringeri only has very weak shell constrictions in the juvenile stage, while S. subbilobatus has distinct shell constrictions. In this feature, S. voehringeri also differs from S. intermedius , which has no constrictions.

Figures

Fig. 7. Early Tournaisian representative ammonoids of the family Prionoceratidae from the Hasselbachtal section, all Weyer 1993–1994 Coll. A. Mimimitoceras hoennense Korn, 1993, specimen MB.C.5241.2 from bed 59. B. Globimitoceras globiforme (Vöhringer, 1960), specimen MB.C.5240.7 from bed 57. C. Stockumites voehringeri sp. nov., paratype MB.C.5235.1 from bed 46. [Illustrated by Korn & Weyer (2003, pl. 1 figs 1–2) as Acutimitoceras cf. intermedium.] D. Stockumites intermedius (Schindewolf, 1923), specimen MB.C.5248.1 from bed 77. E. Stockumites convexus (Vöhringer, 1960), specimen MB.C.5241.1 from bed 59. F. Stockumites parallelus sp. nov., paratype MB.C.5247.2 from bed 57. (Illustrated by Korn & Weyer 2003: pl. 2 figs 6–7, as Acutimitoceras subbilobatum.) Scale bar units =1 mm.

Fig. 42. Stockumites voehringeri sp. nov. from the Oberrödinghausen railway cutting; all Vöhringer Coll. A. Holotype GPIT-PV-63995 from unknown bed. B. Paratype GPIT-PV-63885 from bed 3b. C. Paratype GPIT-PV-64005 from bed 2. D. Paratype GPIT-PV-63850 from bed 3e. Scale bar units =1 mm.

Fig. 43. Stockumites voehringeri sp. nov. from the Oberrödinghausen railway cutting. A. Paratype MB.C.31107.1 (Weyer 1993–1994 Coll.) from bed 3b. B. Paratype MB.C.31111.1 (Weyer 1993–1994 Coll.) from bed 3d2b. C. Paratype MB.C.31101.1 (Korn 1977 Coll.) from unknown bed. D. Paratype MB.C.31101.2 (Korn 1977 Coll.) from unknown bed. E. Paratype MB.C.31105 (Korn 1977 Coll.) from unknown bed. F. Paratype MB.C.31109.1 (Weyer 1993–1994 Coll.) from bed 3d1. G. Paratype MB.C.31110.1 (Weyer 1993–1994 Coll.) from bed 3d1b. Scale bar units=1 mm.

Fig. 44. Stockumites voehringeri sp. nov. from the Oberrödinghausen railway cutting. A. Cross section of paratype MB.C.31111.2 (Weyer 1993–1994 Coll.) from bed 3d2. B. Suture line of paratype MB.C.31111.3 (Weyer 1993–1994 Coll.) from bed 3d2, at dm=20.0 mm, ww =13.1 mm, wh=12.6 mm. C. Suture line of paratype GPIT-PV-63885 (Vöhringer Coll.) from bed 3b, at ww =20.5 mm, wh =17.5 mm. D. Course of the internal shell thickenings of paratype GPIT-PV-63850 (Vöhringer Coll.) from bed 3e, at dm =34.0 mm, ww =17.0 mm, wh= 21.5 mm. E. Course of the internal shell thickenings of holotype GPIT-PV-63995 (Vöhringer Coll.) from unknown bed of Oberrödinghausen, at dm =40.0 mm, ww =20.5 mm, wh =22.0 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.

Fig. 45. Stockumites voehringeri sp. nov. from the Oberrödinghausen railway cutting. A. Cross section of paratype MB.C.31099.1 (Vöhringer Coll.) from bed 4. B. Cross section of paratype MB.C.31112.1 (Weyer 1993–1994 Coll.) from bed 3e. Scale bar units=1 mm.