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 Trimaenioceras fuscina gen. et sp. nov. urn:lsid:zoobank.org:act: C5B0E733-6BD9-48EB-A89A-009451C83B6F Fig. 15 ; Table 12 Diagnosis Species of Trimaenioceras gen. nov. with thinly discoidal and subinvolute conch at 20 mm dm (ww/dm ~ 0.40; uw/dm ~ 0.15) with weakly compressed whorl profile (ww/wh ~ 0.85) and low coiling rate (WER ~ 1.70). Whorl profile at 20 mm conch diameter horseshoe-shaped with flattened subparallel flanks, rounded ventrolateral shoulder and rounded venter. Ventrolateral shoulder without spiral groove. Growth lines very fine. Suture line with wide external lobe, moderately deep, cuneiform E 2 lobe, rounded ventrolateral saddle and V-shaped, acute lateral lobe. Etymology After the Latin nomen ‘ fuscina ’ = ‘trident’, because of the shape of the external lobe. Type material Holotype MOROCCO • Anti-Atlas , south-eastern Tafilalt , Hassi Nebech , section 2; middle Givetian ; Bockwinkel and Ebbighausen 2002–2004 Coll.; MB.C.31970.1 (illustrated in Fig. 14B ). Paratype MOROCCO • 1 spec. ; same collection data as for holotype; MB.C.31970.2 (illustrated in Fig. 14A ). Fig. 15. Trimaenioceras fuscina gen. et sp. nov. from Jebel Ouaoufilal. A . Paratype MB.C.31970.2. B . Holotype MB.C.31970.1. C . Paratype MB.C.31970.2; suture line at wh = 9.5 mm. Scale bar units = 1 mm. Table 12. Conch dimensions (in mm) and ratios of Trimaenioceras fuscina gen. et sp. nov.

specimen	dm	ww	wh	uw	ah	ww/dm	ww/wh	uw/dm	WER	IZR
MB.C.31970.2	21.3	8.5	10.2	2.9	5.1	0.40	0.83	0.14	1.73	0.50
MB.C.31970.1	20.8	8.8	9.9	3.2	4.9	0.42	0.89	0.15	1.71	0.51

Description Holotype MB.C.31970.1 is a fully septate internal mould of a specimen with 21 mm conch diameter ( Fig. 15B ). The conch is thinly discoidal with a rather small umbilicus (ww/dm = 0.42; uw/dm = 0.15); a weakly compressed whorl profile (ww/wh = 0.89) and a low coiling rate (WER = 1.71). The specimen shows that the umbilicus is being narrowed, caused by increased overlap of the flanks upon the umbilicus, during the last preserved volution. Paratype MB.C.31970.2 is a specimen with 21.5 mm conch diameter ( Fig. 15A ), which in size and proportions of the conch closely resembles the holotype (ww/dm = 0.40; uw/dm = 0.14). The suture line shows a very wide external lobe that is subdivided into three almost equally wide and deep prongs, of which the E 2 lobes are asymmetric and cuneiform. The median saddle reaches about two thirds of the depth of the external lobe. The ventrolateral saddle is nearly symmetric and inclined towards the venter; the lateral lobe is V-shaped with gently convex flanks ( Fig. 15C ). The last phragmocone volution has about 16 chambers. Remarks Trimaenioceras fuscina gen. et sp. nov. is the species of the genus with the most slender conch. At about 20 mm conch diameter, its ww/dm ratio is ~0.40, while it is~ 0.50 in T. klugi gen. et sp. nov. and T. eculeus gen. et sp. nov. Trimaenioceras fuscina differs from T. klugi in the less deep sutural elements of the external lobe. A suture line very similar to T. fuscina can be seen in T. eculeus , but this species differs in the wider umbilicus (uw/dm~ 0.20) at 20 mm conch diameter (uw/dm is only ~ 0.15 in T. fuscina ).