The tornoceratid ammonoids from the Roteisenstein Formation of Dillenburg (Cephalopoda, Ammonoidea) Author Korn, Dieter 304FF76E-83FB-478C-AAA9-BD5769C80918 Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, D- 10115 Berlin, Germany. dieter.korn@mfn.berlin Author Bockwinkel, Jürgen 1F1EDD42-B1CE-425C-9CBD-D19658A6C453 Dechant-Fein-Strasse 22, D- 51375 Leverkusen, Germany. jbockwinkel@t-online.de text European Journal of Taxonomy 2022 2022-03-21 806 32 51 http://zoobank.org/a2b2a310-8c8c-41b0-b934-1666129b7d90 journal article 20137 10.5852/ejt.2022.806.1699 ee706a5b-3456-4097-b44d-2ebfd40a0824 2118-9773 6373961 A2B2A310-8C8C-41B0-B934-1666129B7D90 Tornoceras typus (Sandberger & Sandberger, 1851) Fig. 4 ; Table 1 Goniatites retrorsus var. typus Sandberger & Sandberger, 1851: 109 , pl. 10 fig. 14. Tornoceras simplex Mut. typus – Holzapfel 1895: 98 , text-fig. 6, pl. 6 fig. 11, pl. 7 fig. 9. Tornoceras typus – Korn 2021b: 149 , text-figs 2–5, 6a. Tornoceras typum – Becker 1993: 182 , pl. 3 figs 1–2. — Korn & Klug 2002: 156 , text-fig. 139. ? Goniatites retrorsus var. typus – Sandberger & Sandberger 1851: pl. 10a figs 3–6, 10–11. ? Tornoceras simplex – Foord & Crick 1897: 69 , 107, text-figs 25d–f, 48. ? Tornoceras simplex mut. ovata – Frech 1902b: 47 , pl. 3 fig. 21. non Tornoceras typum – Becker 1993: 182 , pl. 3 figs 3–4, text-fig. 68a. — Becker et al. 2000: pl. 2 figs 7–8. — Korn & Klug 2002: 156 , text-fig. 143a–c. non Tornoceras simplex – Frech 1902: 47, pl. 5 fig. 8. — Wedekind 1918: 135 , pl. 16 fig. 12, textfig. 40a. Diagnosis Tornoceras reaching about 90 mm conch diameter. Thickly pachyconic, subevolute early juvenile stage (ww/dm ~ 0.80; uw/dm ~ 0.35 at 2 mm dm), thickly discoidal and involute subadult stage (ww/ dm ~ 0.58; uw/dm ~ 0.08 at 10 mm dm), thinly discoidal and involute adult stage (ww/dm ~ 0.42; umbilicus closed at 30 mm dm). Whorl profile as wide as high in the subadult stage (ww/wh ~ 1.00 at 10 mm dm) and strongly compressed in the adult stage (ww/wh ~ 0.75 at 30 mm dm); whorl expansion rate very high in the subadult and adult stage (WER = 2.30-2.45). Flanks convex, convergent, umbilical margin continuously rounded. Without any ventrolateral grooves. Suture line with broadly rounded, asymmetric adventive lobe and high ventrolateral saddle. Type material Lectotype GERMANY • Rhenish Mountains , Oberscheld ; probably middle Frasnian (Adorf Limestone) ; designated by Becker (1993) ; figured by Sandberger & Sandberger (1850 –1856: pl. 10 fig. 14), Becker (1993 : pl. 3 figs 1–3) and Korn (2021b : text-fig. 2), re-illustrated here in Fig. 4 ; specimen 53a; Wiesbaden Museum . Additional material examined GERMANY • 1 spec. ; Rhenish Mountains , Oberscheld ; middle Frasnian (Adorf Limestone) ; Erbreich Coll.; MB.C.4466 • 1 spec. ; Rhenish Mountains , Oberscheld ; middle Frasnian (Adorf Limestone) ; Koch Coll.; MB.C.30409 • 1 spec. ; Rhenish Mountains , Dillenburg , Eiserne Hand (Grube Friedrich); middle Frasnian (Adorf Limestone) ; MB.C.30410 . Fig. 4. Tornoceras typus (Sandberger & Sandberger, 1851) , reproduction of the lectotype illustrations by Sandberger & Sandberger (1850 –1856, pl. 10 fig. 14) and the photography by M.R. House in Becker (1993 , pl. 3 figs 1–2). Scale bar units = 1 mm. Table 1. Conch dimensions and ratios of Tornoceras typus (Sandberger & Sandberger, 1851) , lectotype (Wiesbaden 53a).

Specimen	dm	ww	wh	uw	ah	ww/dm	ww/wh	uw/dm	WER	IZR
Wiesbaden 53a	46.0	18.3	29.7	0.0	15.2	0.40	0.62	0.00	2.23	0.49

Description Lectotype 53a (Wiesbaden Museum) Fairly well-preserved specimen with 46 mm conch diameter in red limestone; it is largely chambered and the last half volution belongs to the body chamber ( Fig. 4 ). It is a thinly discoidal conch (ww/ dm = 0.40) with a closed umbilicus. The body chamber is obviously slightly distorted, resulting in a stronger convergence of the flanks (as shown in the original illustration by Sandberger & Sandberger 1850 –1856). Parts of the specimen are covered by shell material, which, however, is not well preserved and does not allow a detailed examination of the ornamentation. The suture line has a small, V-shaped outer lobe and a broadly rounded ventrolateral saddle. The adventitious lobe is twice as deep as the outer lobe and as deep as it is wide; it is broadly rounded and slightly asymmetric. Remarks The species has been discussed several times in the literature. A detailed revision and discussion was carried out by Korn (2021b) ; in this paper both the taxonomic problems and the conch morphology as well as the ontogenetic development are presented on the basis of further material from the Rhenish Mountains.