Koenenites lamellosus (Sandberger & Sandberger, 1851)

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 : 35-39

Koenenites lamellosus (Sandberger & Sandberger, 1851)

Figs 16–18

Goniatites lamellosus Sandberger & Sandberger, 1851: 88 , pl. 8 fig. 1, 1a–d.

? Goniatites Höninghausi – von Buch 1832: 40, pl. 2 figs 3–4. — Bronn 1835: 107, pl. 1 fig. 1. Goniatites sublamellosus Sandberger & Sandberger 1851: 87 , pl. 2 fig. 2, 2a–c. Koenenites lamellosus – Wedekind 1913: 42; 1918: 126. — Matern 1931: 74, pl. 2 fig. 7. — House 1978: 48, pl. 7 figs 3, 5. — Dzik 2002: text-figs 50a–e, 56c–h. — Korn & Klug 2002: 118, text-fig. 118a–b.

Koenenites sublamellosus – Wedekind 1918: 126. — Matern 1931: 74. — Korn & Klug 2002: 118, text- fig. 118c.

non Koenenites lamellosus – Petter 1959: 157, pl. 10 fig. 14, text-fig. 41a.

Diagnosis

Species of Koenenites reaching about 90 mm conch diameter with thickly discoidal, evolute conch at 5 mm dm (ww/dm ~ 0.50; uw/dm ~ 0.45); coiling rate moderate (WER ~ 1.85); with thinly discoidal, subinvolute conch at 20 mm dm (ww/dm ~ 0.40; uw/dm ~ 0.28); with extremely discoidal, subinvolute conch at 75 mm dm (ww/dm ~ 0.25; uw/dm ~ 0.23); coiling rate moderate at 5 mm dm (WER ~ 1.85) and very high above 30 mm dm (WER ~ 2.40). Whorl profile compressed (ww/wh ~ 0.50) in the adult stage; umbilical wall steep and rounded, venter rounded. Growth lines lamellar, strongly biconvex with very narrow, high ventrolateral projection. Suture line simple, with V-shaped external lobe, high median saddle, pointed asymmetrical prongs of the E lobe, slightly asymmetrically rounded lateral saddle and pointed L lobe.

Material examined

Lectotype GERMANY • Rhenish Mountains, Nanzenbach ; early Frasnian (Red Ironstone); Wiesb. 40a. Illustrated by Sandberger & Sandberger (1850 –1856: pl. 8 fig. 1) and Korn & Klug (2002: text-fig. 108a), reillustrated here in Fig. 16A .

Paralectotype GERMANY • Rhenish Mountains, Nanzenbach ; early Frasnian (Red Ironstone); Wiesb. 40b. Illustrated by Sandberger & Sandberger (1850 –1856: pl. 8 fig. 1a-c) and Korn & Klug (2002: text-fig. 108b), reillustrated here in Fig. 16D .

Additional material

GERMANY • 4 specimens; Rhenish Mountains , Oberscheld ( Grube Anna ); early Frasnian (Red Ironstone); Koch Coll.; MB.C.4306.1 , MB.C.34306.2 , MB.C.4306.3 , MB.C.22184 • 1 specimen; Rhenish Mountains , Oberscheld (Grube Königszug, 120 m-Sohle); early Frasnian (Red Ironstone); MB.C.22201 • 2 specimens; Rhenish Mountains , Oberscheld ( Grube Rinkenbach ); early Frasnian (Red Ironstone); Dannenberg Coll.; MB.C.22183 , MB.C.22189a–b • 1 specimen; Rhenish Mountains , Oberscheld (Sessacker); early Frasnian (Red Ironstone); Dannenberg Coll.; MB.C.30431 • 2 specimens; Rhenish Mountains , Oberscheld (Staatliche Grube); early Frasnian (Red Ironstone); Hubach 1913 Coll.; MB.C.4303.2 , MB.C.4303.3 .

Description

Eight specimens are selected for description and illustration:

Lectotype Wiesb. 40a: incomplete specimen with 65 mm conch diameter in haematitic ironstone ( Fig. 16A ).

Paratype Wiesb. 40b: incomplete specimen with about 50 mm conch diameter in haematitic ironstone ( Fig. 16D ).

MB.C.22184: incomplete specimen with 73 mm conch diameter in haematitic iron ore, the last whorl is partly crushed ( Fig. 17A ).

MB.C.22183: incomplete specimen with 53 mm conch diameter in haematitic ironstone ( Fig. 17B ).

MB.C.22201: sectioned specimen with 77 mm conch diameter in haematite ore ( Fig. 18A ).

MB.C.4306.1: well-preserved, complete steinkern specimen with 36 mm conch diameter in haematitic ironstone ( Fig. 17C ).

MB.C.4306.2: well-preserved, complete specimen with 25 mm conch diameter in haematitic ironstone, ornament perfectly preserved ( Fig. 17D ).

MB.C.4306.3: well-preserved, complete specimen with 20 mm conch diameter in haematitic ironstone, ornament perfectly preserved ( Fig. 17E ).

The three specimens MB.C.4306.1, MB.C.4306.2 and MB.C.4306.3 allow the study of conch proportions and ornament between 19 and 36 mm diameter ( Fig. 17 C-E). They are similar in shape with a weak ontogenetic trend towards a slenderer conch (ww/dm decreasing from 0.35 to 0.29). They show an oblique, broadly convex umbilical wall and flanks that converge slowly towards the narrowly rounded venter. The ornament shows lamellar growth lines, which in the two smaller specimens MB.C.4306.2 and MB.C.4306.3 are particularly well-preserved; they extend with a low dorsolateral projection, a deep and wide lateral sinus and a very narrow, very high linguiform ventrolateral projection across the flanks and then turn back to form a narrow, very deep ventral sinus.

The larger specimens MB.C.22183 (53 mm dm) and MB.C.22184 (73 mm dm) are thinly discoidal and subinvolute with a compressed whorl profile; the umbilical wall is steep and the flanks converge towards the narrowly rounded venter ( Fig. 17A–B ). The ornament shows biconvex growth lines,

which are fine on the inner flank and lamellar on the outer flank. They extend with a moderately high dorsolateral projection and a high and subangular ventrolateral projection. The external sinus is deep and semicircular. The suture line is partly visible in specimen MB.C.22184, showing a V-shaped lateral lobe on the inner flank ( Fig. 18B ).

The sectioned specimen MB.C.22201 ( Fig. 18A ) shows significant ontogenetic changes in the conch parameters: (1) the ww/dm ratio has a nearly monophasic ontogeny with a rather continuous decrease from 0.75 at 1 mm dm to = 0.25 at 77 mm dm. (2) The ww/wh ratio has a similar course (from 2.05 to 0.50) but with more accelerated decrease between 3 and 10 mm dm. (3) The uw/dm ratio is conspicuously biphasic with a juvenile increase from 0.35 to 0.45 at 5 mm dm and an adult decrease to 0.23. (4) The coiling rate is also biphasic, but not parallel to the uw/dm ratio; the WER shows a juvenile decrease

to 1.68 at 3.5 mm dm, followed by a decelerated increase with asymptotic approximation of a value of 2.40 at 30 mm dm ( Fig. 18C–F ). The ontogeny of the whorl profile is rather simple with a continuous transformation of a depressed shape into a compressed shape; the value falls below a value of 1.00. Above this diameter, the whorl profile has a steep umbilical wall, a broadly rounded umbilical margin, moderately strong converging flanks and a rounded venter.

Remarks

Matern (1931: 74, pl. 2 fig. 7) proposed a neotype from the Senckenberg Collection (specimen XI329a) and stated that the original specimen is missing. However, two syntypes figured by Sandberger & Sandberger (1850 –1856) are preserved (specimens 40a = old 62.11./W.15a and 40b = old 62.11./W.15b) in the Sandberger collection, which is stored at the Wiesbaden Museum. House (1978: 48, pl. 7 fig. 5) designated specimen 40a as the lectotype; it was illustrated by Sandberger & Sandberger (1850 –1856: pl. 8 fig. 1) and is re-illustrated here ( Fig. 16A ).

Sandberger & Sandberger (1850 –1856) described the two new species “ Goniatites sublamellosus ” and “ Goniatites lamellosus ”, which apparently are conspecific. Of these two, mostly “ G. lamellosus ” was refigured and is therefore here used as the valid species (despite the page priority of “ G. sublamellosus ”).

Figures

Fig. 16. Koenenites lamellosus (Sandberger & Sandberger, 1851). A. Lectotype 40a in the Wiesbaden collection from Nanzenbach. B. Lectotype 40a, reproduction of the figure of Sandberger & Sandberger (1850–1856: pl. 8 fig. 1). C. Probably lost specimen, original of “Goniatites sublamellosus”, reproduction of the figure of Sandberger & Sandberger (1850–1856: pl. 6 fig. 2, 2a). D. Paratype 40b in the Wiesbaden collection from Nanzenbach. E. Paratype 40b, reproduction of the figure of Sandberger & Sandberger (1850–1856: pl. 8 fig. 1a–1c). F. Suture line of paratype 40b, reproduction of the figure of Sandberger & Sandberger (1850–1856: pl. 8 fig. 1d). Scale bar units = 1 mm.

Fig. 17. Koenenites lamellosus (Sandberger & Sandberger, 1851). A. Specimen MB.C.22184 (Koch Coll.) from Oberscheld (Anna Mine). B. Specimen MB.C.22183 (Dannenberg Coll.) from Oberscheld (Rinkenbach Mine).C. Specimen MB.C.4306.1 (Koch Coll.) from Oberscheld (Anna Mine). D. Specimen MB.C.4306.2 (Koch Coll.) from Oberscheld (Anna Mine). E. Specimen MB.C.4306.3 (Koch Coll.) from Oberscheld (Anna Mine). Scale bar units = 1 mm.

Fig. 18. Koenenites lamellosus (Sandberger & Sandberger, 1851). A. Cross section of specimen MB.C.22201 from Oberscheld (Königszug Mine). B. Suture line of specimen MB.C.22184 (Koch Coll.) from Oberscheld (Anna Mine), at dm = 29.0 mm, ww = 7.4 mm, wh = 11.1 mm. C–F. Ontogenetic trajectories of the cardinal conch parameters. Scale bar units = 1 mm.