Bouhamedites, Korn & Bockwinkel & Ebbighausen & Klug, 2003

Korn, Dieter, Bockwinkel, Jürgen, Ebbighausen, Volker & Klug, Christian, 2003, Palaeobiogeographic and evolutionary meaning of an early Late Tournaisian ammonoid fauna from the Tafilalt of Morocco, Acta Palaeontologica Polonica 48 (1), pp. 71-92 : 86-87

Bouhamedites gen. nov.

Derivation of name:AfterKsarBouhamed,wherethefaunawasfound.

Type species: Bouhamedites enigmaticus sp. nov.

Diagnosis.—Pericyclid with small thickly discoidal conch. Umbilicus almost closed and umbilical margin broadly rounded. Aperture and whorl expansion rate moderately high ( WER 2.0). Ornament with fine, slightly biconvex riblets. Suture line with wide, V−shaped external lobe and low median saddle. Ventrolateral saddle asymmetrical, widely rounded. Rounded adventive lobe.

Comparisons.— Bouhamedites gen. nov. displays a morphology that is not known from any other Middle or Late Tournaisian ammonoid, and hence assignment to the family Pericyclidae is uncertain. Some similarities exist with involute species of Goniocyclus Gordon, 1986 , but in these, the ribs are much sharper and form an angular ventral sinus.

Occurrence.—So far only known from the vicinity of Jebel Ouaoufilal; Oued Znaïgui Formation, early Late Tournaisian. Bouhamedites enigmaticus sp. nov.

Figs. 23H, 27 .

Derivation of name: After the enigmatic conch morphology and ornament.

Holotype: Specimen MB.C.3987 (coll. Bockwinkel and Ebbighausen), Fig. 23H.

Type locality and horizon: Taouz, Jebel Ouaoufilal, locality B east of Ksar Bouhamed (Tafilalt, Morocco); Oued Znaïgui Formation, early Late Tournaisian.

Material.—One complete phragmocone, almost 10 mm in diameter.

Diagnosis.— Bouhamedites with pachyconic conch at 9 mm diameter (ww/dm 0.62). Umbilicus very narrow (uw/dm 0.05), umbilical margin rounded. Ornament with approximately 80 smooth riblets per volution, forming a shallow lateral and deeper sinus across the venter. Suture line with wide, V−shaped external lobe, low median saddle, broadly rounded ventrolateral saddle, and asymmetrical adventive lobe.

Description.—The almost involute, pachyconic conch is widest at the umbilicus, from where the flanks converge to a broadly rounded venter. The steinkern of the holotype displays approximately 80 shallow ribs on the venter which cause a regular undulation. They are strongest on the venter where they form shallow and wide sinuses. They wedge out in the midflank area. Their course is slightly biconvex with a barely visible lateral sinus and a low ventrolateral projection.

The holotype MB.C.3987 ( Fig. 27 ) shows a suture line that differs markedly from all the other Late Tournaisian ammonoids. The external lobe is V−shaped and wide, and its prongs are narrowly rounded at their base. It is divided by a low median saddle. The ventrolateral saddle is widely rounded, and continues into the symmetric, rounded adventive lobe. On the last volution, the septa are periodically approximated .

Dimensions.—(in mm).

ww/ ww/ uw/ dm ww wh uw ah WER IZR dm wh dm holotype 9.34 5.77 5.02 0.57 2.78 2.02 0.62 1.15 0.06 0.52 MB .C.3987

Comparisons.— Bouhamedites enigmaticus sp. nov. is clearly distinct from the other species in the Ksar Bouhamed fauna, and it is not clear that it belongs to the pericyclids. Superficially, the conch resembles Irinoceras , but the suture line is very different.

Figures

Fig. 27. Suture line of Bouhamedites enigmaticus gen. et sp. nov.; holotype MB.C.3987 at dm 8.9 mm, ww 5.6 mm, wh 4.9 mm; × 10.