Afromaenioceras brumale, 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 : 21-23

Afromaenioceras brumale sp. nov.

urn:lsid:zoobank.org:act:A55F968F-58F4-48D2-9D54-B3CD46403010

Fig. 11 ; Table 8

? Maenioceras cf. crassum – Bensaïd 1974: 105, pl. 1 fig. 10, 10a.

? Afromaenioceras n. sp. – Becker et al. 2004: pl. 1 figs 7–8.

Diagnosis

Species of Afromaenioceras with thinly pachyconic and subevolute conch at 6 mm dm (ww/dm~ 0.70; uw/dm~ 0.38); conch thickly discoidal and subinvolute at 16 mm dm (ww/dm~0.55; uw/dm~0.18) with weakly depressed whorl profile (ww/wh ~ 1.15) and low coiling rate (WER ~1.55). Whorl profile at 16 mm conch diameter C-shaped with convex, weakly convergent flanks, broadly rounded ventrolateral shoulder and rounded venter. Ventrolateral shoulder with faint spiral groove. Growth lines coarse, strongly biconvex. Suture line with wide external lobe, small, subangular E 2 lobe, inverted U-shaped ventrolateral saddle and symmetric, blunt V-shaped lateral lobe.

Etymology

After the Latin adjective ‘ brumalis, - e ’ = ‘summery’; the conch resembles a summer tire.

Type material

Holotype

MOROCCO • Anti-Atlas , Oufrane-E ; bed 12, middle Givetian ; Bockwinkel and Ebbighausen 2002– 2004 Coll.; MB.C.31960 (illustrated in Fig. 11A ).

Paratypes

MOROCCO • 25 specs; Anti-Atlas , Oued Mzerreb-W ; beds 10/11, middle Givetian; Bockwinkel and Ebbighausen 2004 Coll.; MB.C.31962.1 to MB.C.31962.25 • 1 spec.; Anti-Atlas , Tafilalt , Jebel Ouaoufilal ; middle Givetian; Bockwinkel and Ebbighausen 2004 Coll.; MB.C.31961 • 6 specs; Anti-Atlas , Oufrane-E ; bed 11, middle Givetian; Bockwinkel and Ebbighausen 2004 Coll.; MB.C.31963.1 to MB.C.31963.6 • 1 spec.; Anti-Atlas , Tiguisselt ; bed 10, middle Givetian; Bockwinkel and Ebbighausen 2004 Coll.; MB.C.31964 .

Description

Holotype MB.C.31960 is a very well-preserved limonitic internal mould with 16 mm conch diameter ( Fig. 11A ). It is a thickly discoidal, subinvolute conch (ww/dm = 0.55; uw/dm = 0.18) with a weakly depressed whorl profile (ww/wh = 1.16) and a low coiling rate (WER = 1.53); flanks and venter are broadly rounded. The ventrolateral shoulder has a faint spiral groove. Traces of coarse growth lines are visible on the flanks. The last volution of the phragmocone has only ten chambers.

Paratype MB.C.31961 is a thickly discoidal, subinvolute conch with 16 mm conch diameter and shows, like the two specimens described above, rows of Housean Pits in the outer flank region ( Fig. 11B ).

Paratype MB.C.31962.4 was sectioned ( Fig. 11F ) and shows two volutions up to a conch diameter of 8.2 mm. Between 5 and 8 mm conch diameter, the whorl profile changes from crescent-shaped to C-shaped and the conch becomes more slender and narrowly umbilicate.

Paratypes MB.C.31962.2 ( Fig. 11D ) and MB.C.31962.3 ( Fig. 11E )

Suture lines were drawn from those at wh = 4.5 and wh = 3.8 mm, respectively. Both show the Y-shaped external lobe with stair-shape flanks. However, they differ in the shape of the ventrolateral saddle, which is narrower in paratype MB.C.31962.2, and in the shape of the lateral lobe, which is blunt V-shaped in paratype MB.C.31962.2, but nearly U-shaped in paratype MB.C.31962.3.

Remarks

Afromaenioceras crassum is a similar species but differs in the stouter conch (ww/dm~0.65; ww/wh~1.45; uw/dm 0.24) from A. brumale sp. nov. (ww/dm~0.55; ww/wh ~1.15; uw/dm 0.25) at~ 15 mm dm.

Figures

Fig. 11. Afromaenioceras brumale sp. nov. A. Holotype MB.C.31960 from Oufrane-E, bed 12. B. Paratype MB.C.31961 from, Jebel Ouaoufilal. C. Paratype MB.C.31962.1 from Oued Mzerreb-W, beds 10/11. D. Paratype MB.C.31962.2 from Oued Mzerreb-W, bed 10/11; suture line at wh = 4.5 mm. E. Paratype MB.C.31962.3 from Oued Mzerreb-W, beds 10/11; suture line at wh = 3.8 mm. F. Paratype MB.C.31962.4 from Oued Mzerreb-W, bed 10/11; cross section. Scale bar units = 1 mm.