Ammonoids of the Middle Devonian family Maenioceratidae in the Anti-Atlas of Morocco Author Bockwinkel, Jürgen F7FE7EEA-B678-4FEE-879C-8C429F66BF3A Dechant-Fein-Strasse 22, 51375 Leverkusen, Germany. j.bockwinkel@t-online.de Author Korn, Dieter 286CA4F3-7EBC-4AEF-A66A-B2508D001367 Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, 10115 Berlin, Germany. dieter.korn@mfn.berlin text European Journal of Taxonomy 2024 2024-01-30 921 1 1 35 https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2413/10641 journal article 10.5852/ejt.2024.921.2413 2118-9773 10590243 80B3C408-DD2C-4373-96AE-15F067D723F8 Maenioceras beckeri sp. nov. urn:lsid:zoobank.org:act: 48EAD7CA-D85E-40E0-B32C-7A6C5A078A7C Fig. 7 ; Table 4 Maenioceras excavatum – Petter 1959: 124 , pl. 6 fig. 11. ? Maenioceras cf. excavatum – Petter 1959: 125 , pl. 6 fig. 13. — Bensaïd 1974 : pl. 2 fig. 5. ? Maenioceras n. sp. III – Becker et al . 2004 : pl. 1 figs 11–12. Diagnosis Species of Maenioceras with thickly discoidal and subinvolute conch at 17 mm dm (ww/dm ~0.50; uw/dm ~ 0.30) with weakly depressed whorl profile (ww/wh ~ 1.20) and low coiling rate (WER~ 1.55). Whorl profile at 17 mm conch diameter horseshoe-shaped with flattened, nearly parallel, weakly convergent flanks, subangular ventrolateral shoulder and broad, nearly flat venter. Ventrolateral shoulder with a faint groove in adult specimens. Growth lines coarse, strongly biconvex. Suture line with extremely wide external lobe, deep, U-shaped E 2 lobe, inverted U-shaped ventrolateral saddle and blunt, tongue-shaped lateral lobe. Etymology Named after R. Thomas Becker, who possibly already recognised this species as new. Type material Holotype MOROCCO • Anti-Atlas , Hassi Nebech , section 2; middle Givetian ; Bockwinkel and Ebbighausen Coll.; MB.C.31952.1 (illustrated in Fig. 7A ). Paratypes MOROCCO • 2 specs; same collection data as for holotype; MB.C.31952.2 , MB.C.31952.3 . Description Holotype MB.C.31952.1 is a limonitic internal mould of a fully chambered specimen (Fig, 7A) with 17 mm conch diameter; it is rather well-preserved only on the right side. The conch is thickly discoidal and subinvolute (ww/dm = 0.49; uw/dm = 0.24) with low coiling rate (WER = 1.57). The whorl profile is weakly depressed (ww/wh = 1.18) with slightly convex flanks. The ventrolateral shoulder forms a rather distinct margin separating the flanks and the almost flat, but slightly convex venter. The growth lines are bundled with a strongly biconvex course. The suture line is somewhat unusual for Maenioceras with an extremely wide external lobe and a symmetrically rounded E 2 lobe that is half as deep as the E 1 lobe. On the flank follow a narrowly rounded asymmetrical ventrolateral saddle and a deep, tongue-shaped lateral lobe (Fig, 7C). Fig. 7. Maenioceras beckeri sp. nov. from Hassi Nebech. A . Holotype MB.C.31952.1. B . Paratype MB.C.31952.2. C . Holotype MB.C.31952.1; suture line at wh = 6.4 mm. Scale bar units = 1 mm. Table 4. Conch dimensions (in mm) and ratios of Maenioceras beckeri sp. nov.

specimen	dm	ww	wh	uw	ah	ww/dm	ww/wh	uw/dm	WER	IZR
MB.C.31952.1	17.3	8.5	7.2	4.2	3.5	0.49	1.18	0.24	1.57	0.51
MB.C.31952.2	15.2	7.5	7.4	–	–	0.49	1.01	–	–	–
MB.C.31952.3	14.6	6.5	4.7	5.3	3.3	0.45	1.38	0.36	1.67	0.30

Paratype MB.C.31952.2 shows the same conch proportions as the holotype with a ww/dm ratio of 0.49 and an estimated uw/dm ratio of 0.30 at 15 mm dm. Numerous dense growth lines are visible in this specimen (Fig, 7B). Paratype MB.C.31952.3 is, with a ww/dm ratio of 0.45 and a uw/dm ratio of 0.36 at 14.5 mm conch diameter, slightly more slender and more evolute than the other two type specimens. Remarks The deep E 2 lobe in Maenioceras beckeri sp. nov. is the cardinal character to separate the new species from the other species of the genus, which possess a shallow E 2 lobe.