Cymaclymenia subvexa, Klein & Korn, 2014

Klein, C. & Korn, D., 2014, A morphometric approach to conch ontogeny of Cymaclymenia and related genera (Ammonoidea, Late Devonian), Fossil Record 17 (1), pp. 1-32 : 13-15

publication ID	https://doi.org/ 10.5194/fr-17-1-2014
DOI	https://doi.org/10.5281/zenodo.10997808
persistent identifier	https://treatment.plazi.org/id/4D1287FB-CB3C-FFDB-FF98-30E4FAB6F8AB
treatment provided by	Felipe
scientific name	Cymaclymenia subvexa
status	sp. nov.

Treatment

Cymaclymenia subvexa View in CoL n. sp.

Figures 13 View Figure 13 and 14 View Figure 14

1960 Cymaclymenia striata . – Petter, p. 47, pl. 7, figs. 16, 17, 19, pl. 8, figs. 1, 4, 13.

1999 Cymaclymenia cordata . – Korn, p. 170, pl. 4, fig. 5.

Derivation of name: After Lat. subvexus, -a, -um (adj.) = oblique, because of the shape of the umbilical wall.

Holotype: Specimen MB.C.22658 (Rücklin 2003 Coll.); illustrated here in Fig. 13a View Figure 13 .

Type locality and horizon: Bou Ifarherioun 17 km south of Rissani; Gonioclymenia Assemblage (late Famennian).

Material: 383 specimens with a maximum conch diameter of 50 mm.

Diagnosis: Species of Cymaclymenia with thinly discoidal conch in the adult stage (ww / dm = 0.30–0.35); whorl cross section weakly compressed (ww / wh = 0.65). Conch shape in the intermediate stage (10 mm dm) thinly discoidal and subevolute (ww / dm = 0.32; uw / dm = 0.32). Umbilical wall oblique in the adult stage, flanks moderately converging, venter narrowly rounded. Ornament with very fine biconvex growth lines and with weak riblets on the flank.

Discussion: Cymaclymenia subvexa is one of the slender species of the genus. It differs from many of the other species in the presence of riblets on the inner flanks. Of the Uralian species, C. decorata Nikolaeva and Bogoslovsky, 2005 has even stronger and sharper riblets and C. crenata Nikolaeva and Bogoslovsky, 2005 has a rather blunt lateral lobe as well as a stronger biconvex course of the growth lines. C. silesiaca ( Renz, 1914) from Silesia possesses steinkern constrictions at the end of growth.

The new species resembles Procymaclymenia ebbighauseni and Cymaclymenia formosa in conch geometry and ontogeny. P. ebbighauseni is easily separable by the suture line (blunt in P. ebbighauseni , pointed in C. subvexa ), but the differences with C. formosa are less obvious. The two species can best be separated by the form of the umbilical wall, which is oblique in C. subvexa (with an inclination of about 45 ◦) but steep in C. formosa . C. serotina lacks the flank riblets of C. subvexa .