Pseudoprobeloceras pernai ( Wedekind, 1918 )

Korn, Dieter & Bockwinkel, Jürgen, 2022, The early gephuroceratid ammonoids from the Roteisenstein Formation of Dillenburg (Cephalopoda, Ammonoidea), European Journal of Taxonomy 823, pp. 10-47 : 15-19

Pseudoprobeloceras pernai ( Wedekind, 1918)

Figs 4A, C , 5–6

Gephyroceras Pernai Wedekind, 1918: 122 , 166, pl. 21 figs 1–2, text-fig. 28e.

Gephyroceras Barroisi Wedekind, 1918: 122 , 167, pl. 21 fig. 7, text-fig. 28a.

Ponticeras sahlgrundense Matern, 1931: 80 , pl. 2 fig. 12.

Ponticeras pernai pernai – Matern 1931: 79. — House in House & Ziegler 1977: 79, pl. 1 figs 18–22. Pseudoprobeloceras pernai – Korn & Klug 2002: 98.

non Probeloceras pernai – Petter 1959: 153, pl. 11 figs 5–6, text-fig. 40c.

non Ponticeras pernai – House et al. 1985: pl. 1 figs 1–2.

non Pseudoprobeloceras pernai – Bockwinkel et al. 2013a: 10, text-figs 5–6; 2015: 129, text-figs 4b, f–h, 5a–b; 2017: 315, text-figs 4–5.

Diagnosis

Species of Pseudoprobeloceras reaching about 70 mm conch diameter with thinly discoidal, subevolute conch between 30 and 50 mm dm (ww/dm decreasing from ~ 0.30 to ~ 0.25; uw/dm increasing from ~ 0.30 to ~ 0.38); coiling rate moderate (WER ~ 1.95). Whorl profile weakly compressed (ww/wh = 0.65–0.80); umbilical wall oblique, umbilical margin broadly rounded, venter rounded. Growth lines very fine. Suture line with V-shaped external lobe with strongly diverging flanks, median saddle low, E 2 lobe small, rounded or pointed, ventrolateral saddle almost symmetrically rounded, lateral lobe broadly rounded.

Material examined

Lectotype GERMANY • Rhenish Mountains, Oberscheld ( Grube Prinzkessel ); late Givetian (Red Ironstone); Welsch 1912 Coll.; SMF.Mbg.2322 . Illustrated by Wedekind (1918: pl. 21 figs 1–2) and House & Ziegler (1977: pl. 1 figs 21–22); re-illustrated here in Fig. 4A .

Additional material

GERMANY • 1 specimen; Rhenish Mountains , Oberscheld ; late Givetian (Red Ironstone); Erbreich Coll.; MB.C.7696 • 1 specimen; Rhenish Mountains , Oberscheld ( Grube Gründchesseite ); late Givetian (Red Ironstone); Lotz 1901–1902 Coll.; MB.C.30415 • 1 specimen; Rhenish Mountains , Oberscheld (Grube Prinzkessel); late Givetian (Red Ironstone); Fremdling 1922 Coll.; MB.C.4287 • 1 specimen; Rhenish Mountains , Oberscheld (Grube Volpertseiche); late Givetian (Red Ironstone); Bender 1901 Coll.; MB.C.30416 • 3 specimens; Rhenish Mountains , Oberscheld (“Tiefe Grube”); late Givetian (Red Ironstone); Etzold 1910 Coll.; MB.C.22164 , MB.C.30417.1 , MB.C.30417.2 • 1 specimen; Rhenish Mountains , Oberscheld; late Givetian (Red Ironstone); MB.C.30418 • 1 specimen; Rhenish Mountains , Oberscheld (Grube Prinzkessel); late Givetian (Red Ironstone); Welsch 1913 Coll.; SMF.MB.C.2326 .

Description

Seven specimens are selected for description and illustration:

Lectotype SMF. Mbg.2322: rather well-preserved specimen with 38 mm diameter, shell surface and suture line preserved ( Fig. 4A ).

Specimen Mbg.2326, the holotype of “ Gephyroceras Barroisi ”: is a specimen with 51 mm diameter ( Fig. 4C ).

MB.C.22164: fragmentary, somewhat corroded specimen with 53 mm conch diameter in haematitic, micritic limestone; one third of the last volution belongs to the body chamber ( Fig. 5B ).

MB.C.4287: rather complete, somewhat corroded specimen with 46 mm conch diameter in haematitic, sparitic limestone; one quarter of the last volution belongs to the body chamber ( Fig. 5C ).

MB.C.7696: rather complete, somewhat corroded specimen with 45 mm conch diameter in haematitic limestone; one half of the last volution belongs to the body chamber ( Fig. 5D ).

MB.C.30417.1: exfoliated specimen with 37 mm conch diameter in haematitic limestone; only a small part belongs to the body chamber ( Fig. 5E ).

MB.C.30418: deformed but otherwise rather well-preserved specimen with 59 mm conch diameter in haematitic sparitic limestone; conch widely covered with shell. Part of the external suture line visible ( Fig. 5A ).

Lectotype SMF.Mbg.2322 is a specimen with 38 mm diameter ( Fig. 4A ). It is thinly discoidal; the venter is weakly flattened. It is separated, on the last quarter whorl, from the converging flanks by a pronounced ventrolateral shoulder. The specimen has rather coarse growth lines, particularly in inner whorls; they become lamellar on last volution with a high ventrolateral projection.

Specimen SMF.Mbg.2326, the holotype of Pseudoprobeloceras barroisi , is a specimen 51 mm in diameter ( Fig. 4C ). Its umbilical wall is oblique, the flanks converge and the ventrolateral shoulder is prominent. On the last half volution, the specimen shows the transformation from the preadult stage into the adult stage by a rather rapid opening of the umbilicus. The shell ornamentation is poorly preserved.

The additional material allows the study of the proportions, ornamentation and suture lines of the shell in a growth interval between 27 and 59 mm diameter ( Fig. 5 ). In the interval between 30 and 50 mm diameter, the conch becomes slenderer (ww/dm decreasing from ~ 0.35 to ~ 0.25) and more widely umbilicate (uw/dm increasing from ~ 0.30 to ~ 0.28). The coiling rate is moderately high (WER ~ 1.95) at 50 mm dm. The compressed whorl profile (ww/wh decreasing from ~ 0.80 to ~ 0.65) has an oblique umbilical wall, rounded umbilical margin, weakly converging flanks and rounded venter. Shell remains are poorly preserved in the material; the ornament is obviously very weak.

Specimen MB.C.30418 shows the transformation from the pre-adult to adult morphology ( Fig. 5A ). Up to a conch diameter of 45 mm the proportions are similar to the other specimens, but thereafter there is a rapid change in the rate of overlap of the earlier whorls and a reduction in the rate of coiling. Although the specimen is somewhat distorted by tectonics, it shows the differences from the pre-adult stage. At 59 mm conch diameter, the whorl profile is compressed with a rounded umbilical margin, weakly convergent flanks, subangular ventrolateral shoulders and a weakly flattened venter.

Parts of the suture line are visible in several specimens. In specimen MB.C.30417.1 it shows the outline characteristic of the genus with a V-shaped external lobe with strongly diverging flanks, a very low lateral saddle, a deep E 1 lobe and narrowly rounded E 2 lobe. The ventrolateral saddle is almost symmetrical and broadly rounded, the lateral lobe is broadly rounded ( Fig. 6A ).

Remarks

Pseudoprobeloceras barroisi is here synonymised with P. pernai , although its holotype is not well preserved and thus does not allow an accurate description. Up to about 40 mm conch diameter, it closely resembles the typical morphology of P. pernai ; on the last half volution it shows the transformation to the adult morphology with its opened umbilicus.

Pseudoprobeloceras pernai differs from P. applanatum ( Wedekind, 1918) in the shape of the venter; this is rounded in P. pernai , whereas in P. applanatum it is slightly flattened and bordered by a narrow, rounded ventrolateral shoulder on the flanks.

The specimens from Hassi Nebech attributed to P. pernai by Petter (1959), House et al. (1985) and Bockwinkel et al. (2013a) differ by their much higher coiling rate (WER = 2.30–2.45 between 27 and 32 mm dm) from the material from the type region (WER ~ 1.90 at 45 mm dm). They have to be attributed to the species Pseudoprobeloceras nebechense Bensaïd, 1974 , as originally stated by Bensaïd (1974).

Figures

Fig. 4. Specimens of Pseudoprobeloceras Bensaïd, 1974 and Ponticeras Matern, 1929; reproductions from Wedekind (1918). A. Pseudoprobeloceras pernai (Wedekind, 1918), lectotype SMF.Mbg.2322 (Welsch 1912 Coll.) from Oberscheld (Prinzkessel Mine). B. Pseudoprobeloceras applanatum (Wedekind, 1918), holotype SMF.Mbg.2323 (Welsch Coll.) from Oberscheld (Prinzkessel Mine). C. Pseudoprobeloceras pernai (Wedekind, 1918), holotype SMF.Mbg.2326 (Welsch 1913 Coll.) of “Gephyroceras Barroisi” from Oberscheld (Prinzkessel Mine). D. Ponticeras aequabile (Beyrich, 1837), holotype SMF.Mbg.2324 (Meuhsen 1855 Coll.) of “Gephyroceras Kayseri” from Oberscheld (Königszug Mine). Scale bar units = 1 mm.

Fig. 5. Pseudoprobeloceras pernai (Wedekind, 1918). A. Specimen MB.C.30418, probably from Oberscheld. B. Specimen MB.C.22164 (Etzold 1910 Coll.) from Oberscheld (“Tiefe Grube”). C. Specimen MB.C.4287 (Fremdling 1922 Coll.) from Oberscheld (Prinzkessel Mine). D. Specimen MB.C.7696 (Erbreich Coll.) from Oberscheld. E. Specimen MB.C.30417.1 (Etzold 1910 Coll.) from Oberscheld (“Tiefe Grube”). Scale bar units = 1 mm.

Fig. 6. Pseudoprobeloceras pernai (Wedekind, 1918). A. Suture line of specimen MB.C.30417.1 (Etzold 1910 Coll.) from Oberscheld (“Tiefe Grube”), at dm = 27.0 mm, ww = 9.0 mm, wh = 11.0 mm. B. Suture line of specimen MB.C.30418, probably from Oberscheld, at dm = 48.3 mm, ww = 11.9 mm, wh = 15.6 mm. C–F. Ontogenetic trajectories of the cardinal conch parameters. Scale bar units = 1 mm.