Trimaenioceras paucum, Bockwinkel & Korn, 2024

Bockwinkel, Jürgen & Korn, Dieter, 2024, Ammonoids of the Middle Devonian family Maenioceratidae in the Anti-Atlas of Morocco, European Journal of Taxonomy 921 (1), pp. 1-35 : 31-32

Trimaenioceras paucum gen. et sp. nov.

urn:lsid:zoobank.org:act:90C42810-1EF6-4CCC-A8AF-DC841BC9539A

Fig. 16 ; Table 13

Diagnosis

Species of Trimaenioceras gen. nov. with thickly discoidal and involute conch at 14 mm dm (ww/dm~0.60; uw/dm ~0.15) with weakly depressed whorl profile (ww/wh~1.25) and low coiling rate (WER ~1.60). Whorl profile at 14 mm conch diameter C-shaped with convex, convergent flanks, rounded ventrolateral shoulder and rounded venter. Ventrolateral shoulder with faint 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

From the Latin adjective ‘ paucus, - um ’ = ‘poor’, because of the rarity of specimens.

Type material

Holotype

MOROCCO • Anti-Atlas , Tafilalt , Jebel Ouaoufilal ; middle Givetian ; Bockwinkel and Ebbighausen 2004 Coll.; MB.C.31971.1 (illustrated in Fig. 16A ).

Paratype

MOROCCO • 1 spec.; same collection data as for holotype; MB.C.31971.2 (illustrated in Fig. 16B ).

Description

Holotype MB.C.31971.1 is an incomplete internal mould with a conch diameter of 14 mm ( Fig. 16A ). It is thickly discoidal and involute (ww/dm = 0.58; uw/dm = 0.14) with a weakly depressed whorl profile (ww/wh = 1.25) and a low coiling rate (WER = 1.60). The flanks are weakly rounded and converge toward the broadly rounded venter; the ventrolateral shoulder shows a shallow spiral groove. The suture line has a wide external lobe, a moderately deep, asymmetric E 2 lobe, a slightly asymmetric rounded ventrolateral saddle and a wide, pointed L lobe ( Fig. 16C ).

Paratype MB.C.31971.2 ( Fig. 16B ) largely agrees, in its conch morphology, with the holotype.

Remarks

Trimaenioceras paucum gen. et sp. nov. is the only one Trimaenioceras gen. nov. with ventrolateral grooves and thus easily distinguishable from the other species.

Figures

Fig. 16. Trimaenioceras paucum gen. et sp. nov. from Hassi Nebech. A. Holotype MB.C.31971.1. B. Paratype MB.C.31971.2. C. Holotype MB.C.31971.1; suture line at wh = 5.0 mm. Scale bar units = 1 mm.