Lunupharciceras lunulicosta ( Sandberger & Sandberger, 1850 )

Korn, Dieter & Bockwinkel, Jürgen, 2021, The pharciceratid ammonoids from the Roteisenstein Formation of Dillenburg (Cephalopoda, Ammonoidea), European Journal of Taxonomy 771, pp. 1-79 : 47-52

Lunupharciceras lunulicosta ( Sandberger & Sandberger, 1850)

Figs 35–38 ; Tables 21–22

Goniatites lunulicosta Sandberger & Sandberger, 1850: 69 , pl. 3 figs 14, 14a– 14f.

Goniatites (Prolecanites) lunulicosta – Frech 1888: 27, pl. 2 fig. 3.

Prolecanites lunulicosta – Frech 1897: 177 e, fig. 2d; 1902: 64, fig. 21d.

Pharciceras lunulicosta – Wedekind 1918: 127, pl. 20 fig. 6. — Matern 1931: 89. — House & Ziegler 1977: 88, pl. 5 fig. 15.

Lunupharciceras lunulicosta – Korn & Klug 2002: 145, text-fig. 134d (only). — Bockwinkel et al. 2013a: 36, text-figs 35a, 36a (only).

non Pharciceras lunulicosta – Petter 1959: 132, pl. 7 figs 2–4, pl. 26 fig. 4, text-fig. 17.

non Lunupharciceras lunulicosta – Korn & Klug 2002: text-fig. 134b. — Bockwinkel et al. 2013a: 36, text-figs 35b–f, 36b–c.

Diagnosis

Lunupharciceras with thinly discoidal, subevolute conch at 20 mm dm (ww/ dm ~0.35; uw/ dm ~0.35) and extremely discoidal, subevolute conch at 40 mm dm (ww/ dm ~0.30; uw /dm ~0.35). Whorl profile nearly circular (ww/ wh ~ 1.00) at 20 mm dm and compressed at 40 mm dm (ww/ dm ~ 0.70). Umbilical wall steep, umbilical margin rounded, flanks converging to the continuously rounded venter. Whorl profile in the adult stage with weakly concave outer flanks, pronounced ventrolateral shoulder and weakly flattened venter. Adult stage with short ventrolateral riblets. Suture line with parallel-sided, slightly blunt E 2, L, U 2 and U 4 lobes.

Material examined

Lectotype GERMANY • Rhenish Mountains , Oberscheld ; late Givetian (Red Ironstone); Lotz 1901–1902 Coll.; specimen 27c (Wiesbaden Museum), designated by House in House & Ziegler (1977); illustrated by Sandberger & Sandberger (1850 –1856: pl. 3 fig. 14a) and House & Ziegler (1977: pl. 5 fig. 15); Wiesbaden Museum nr. 27c ( Fig. 35C )

Additional material

GERMANY • 2 specimens; Rhenish Mountains , Oberscheld; late Givetian (Red Ironstone); Lotz 1901– 1902 Coll.; 27a, 27b (Wiesbaden Museum) • 2 specimens; Rhenish Mountains , Oberscheld, Beilstein ; late Givetian (Red Ironstone); Beyrich 1835 Coll.; MB.C.3641 , MB.C.5603 • 27 specimens; Rhenish Mountains , Oberscheld (Grube Sahlgrund, 420 m Sohle); late Givetian (Red Ironstone); Kegel 1927 Coll.; MB.C.3642 , MB.C.3648 , MB.C.3666 , MB.C.3667 , MB.C.30250.1 to 30250.23 • 3 specimens; Rhenish Mountains , Oberscheld ; late Givetian (Red Ironstone); Erbreich, Kauth Coll.; MB.C.7690 , MB.C.22121 , MB.C.22171 • 1 specimen; Rhenish Mountains , Oberscheld (Grube Volpertseiche); late Givetian (Red Ironstone); Lotz 1902 Coll.; MB.C.30249 • 1 specimen; Rhenish Mountains , Oberscheld (Westfeld der Grube Königszug, Firste der 120–150 m Sohle); late Givetian (Red Ironstone); Ahlburg Coll.; MB.C.30251 .

Description

Nine specimens are selected for description and illustration:

27a: body chamber fragment with 75 mm conch diameter in dark purple limestone; the specimen was probably used for a combination figured by Sandberger & Sandberger (1850 –1856: pl. 3 fig. 14) ( Fig. 35E ).

27b: incomplete specimen with 57 mm conch diameter in red limestone; the specimen was probably used for a combination figured by Sandberger & Sandberger (1850 –1856, pl. 3 fig. 14) ( Fig. 35A ).

Lectotype 27c: incomplete, rather strongly weathered specimen with 42 mm conch diameter in red limestone; the suture line is visible. The specimen was figured by Sandberger & Sandberger (1850 – 1856: pl. 3 fig. 14a) ( Fig. 35C ).

MB.C.3642: weakly deformed specimen with 57 mm conch diameter in iron-rich micritic limestone; phragmocone filled with sparry calcite. Half of the last whorl belongs to the body chamber, the last suture line is well exposed at the calcite-micrite contact ( Fig. 36A ).

MB.C.3648: fully chambered steinkern specimen of 50 mm conch diameter in weathered iron-rich limestone ( Fig. 36B ).

MB.C.22171: incomplete fully septate specimen with 37 mm conch diameter in red ironstone ( Fig. 36C ).

MB.C.3666: incomplete specimen with 36 mm conch diameter in iron-rich micritic limestone ( Fig. 36D ).

MB.C.3667: incomplete specimen with 30 mm conch diameter in iron-rich micritic limestone ( Fig. 36E ).

MB.C.22121 is sectioned and shows the conch ontogeny from the initial stage up to a conch diameter of 31 mm ( Fig. 37A ).

The cross section of specimen MB.C.22121 demostrates that the trajectories of the conch parameters are very different ( Fig. 37A ): while the ww / dm trajectory is nearly monophasic with a rather continuous decrease from 0.55 at 1 mm dm to 0.33 at 31 mm dm, the uw/ dm trajectory has an irregular undulating course with values ranging between 0.40 and 0.50. The coiling rate is rather high (1.88–2.01) in the early juvenile stage up to 4 mm dm, it is lower (down to 1.64 at 7 mm dm) and shows a subsequent increase to nearly 2.00 at 31 mm dm.

The largest available specimen MB.C.3642 ( Fig. 36A ) with 57 mm conch diameter allows the study of the adult stage. The conch is extremely discoidal and subinvolute with a high coiling rate; the whorl profile is compressed with a steep umbilical wall, subparallel flanks and rounded venter on the first three quarters of the last volution. At the largest diameter of the specimen, the venter is slightly flattened and separated from the flanks by a pronounced ventrolateral shoulder. Shell ornament is not preserved, but at some places, impressions of strengthened growth lines can be seen on the outer flanks. The suture line has, at 35 mm conch diameter, a very wide external lobe with parallel-sided, blunt prongs, a parallelsided, rounded lateral lobe and a smaller U 2 lobe of the same shape ( Fig. 37B ).

Specimen MB.C.3648 ( Fig. 36B ) shows the morphological change from the widely umbilicate juvenile stage to the more involute adult stage. The conch is extremely discoidal and subevolute with high coiling rate; the whorl profile is compressed with a rounded umbilical wall, subparallel flanks and rounded venter. The suture line has, at 42 mm phragmocone diameter, a wide parallel-sided external lobe with lanceolate prongs. Four lobes are visible on the flanks and umbilical wall; while the lateral lobe is lanceolate and acute, the U 2 –U 6 lobes are rounded ( Fig. 37C ).

Specimens MB.C.22171 (37 mm conch diameter), MB.C.3666 (29 mm) and MB.C.3667 (29 mm) demonstrate the decrease of the umbilical width ratio, which parallels the whorl profile becoming more compressed. Specimen MB.C.3666 shows the shell ornament with fine, biconvex growth lines that possess a high ventrolateral projection and a deep ventral sinus, while specimen MB.C.3667 appears to be smooth.

Remarks

Lunupharciceras lunulicosta differs from the co-occurring L. kochi sp. nov. in the narrower umbilicus. Lunupharciceras lunulicosta is subevolute at 20 mm conch diameter (uw / dm ~ 0.40), while L. kochi sp. nov. is still evolute (uw / dm ~ 0.47). At 50 mm conch diameter, the difference is even larger (uw / dm ~ 0.30 in L. lunulicosta but more than 0.40 in L. kochi sp. nov.). The difference in the umbilical width can easily be seen in specimens in which the matrix has been cleaned from the umbilicus.

The material attributed by Bockwinkel et al. (2013a) to L. lunulicosta is fragmentary and difficult to assign. It can therefore not be determined whether it actually belongs to this species.

Figures

Fig. 35. Lunupharciceras lunulicosta (Sandberger & Sandberger, 1850). A. Syntype 27b from Oberscheld in the Wiesbaden Museum. B. Probably a combination of syntypes 27a and 27b in the Wiesbaden Museum, reproduction of the figures in Sandberger & Sandberger (1850–1856: pl. 3 figs 14, 14f). C. Lectotype 27c from Oberscheld in the Wiesbaden Museum. D. Lectotype 27c in the Wiesbaden Museum; reproduction of the figures in Sandberger & Sandberger (1850–1856: pl. 3 fig. 14a, g). E. Syntype 27a from Oberscheld in the Wiesbaden Museum. Scale bar units = 1 mm.

Fig. 36. Lunupharciceras lunulicosta (Sandberger & Sandberger, 1850).A. Specimen MB.C.3642 (Kegel 1927 Coll.) from Oberscheld (Sahlgrund Mine). B. Specimen MB.C.3648 (Kegel 1927 Coll.) from Oberscheld (Sahlgrund Mine). C. Specimen MB.C.22171 (Kauth Coll.) from Oberscheld. D. Specimen MB.C.3666 (Kegel 1927 Coll.) from Oberscheld (Sahlgrund Mine). E. Specimen MB.C.3667 (Kegel 1927 Coll.) from Oberscheld (Sahlgrund Mine). Scale bar units = 1 mm.

Fig. 37. Lunupharciceras lunulicosta (Sandberger & Sandberger, 1850). A. Cross section of specimen MB.C.22121 from Oberscheld. B. Suture line of specimen MB.C.3642 (Kegel 1927 Coll.) from Oberscheld (Sahlgrund Mine), at dm =35.0 mm, ww =10.5 mm, wh =14.5 mm.C. Suture line of specimen MB.C.3648 (Kegel 1927 Coll.) from Oberscheld (Sahlgrund Mine), at dm =42.0 mm, ww =12.5 mm, wh=16.5 mm. D–G. Ontogeneric trajectories of the cardinal conch parameters. Abbreviations: see Material and methods. Scale bar units = 1 mm.

Fig. 38. Lunupharciceras lunulicosta (Sandberger & Sandberger, 1850); reproduction of the specimen illustrated by Frech (1888: pl. 2 fig. 3). Scale bar units = 1 mm.