Rineceras sp. 1

Korn, Dieter & Klug, Christian, 2023, Early Carboniferous coiled nautiloids from the Anti-Atlas (Morocco), European Journal of Taxonomy 885, pp. 156-194 : 160-161

Rineceras sp. 1

Fig. 4A

Material examined

MOROCCO • 2 specimens; Anti-Atlas, north of Gara el Itima, 35 km east-northeast of Taouz ; basal Hamou-Rhanem Formation ; Ebbighausen & Korn 2004 Coll.; MB.C.31293.1–2 .

Description

Specimen MB.C.31293.1 is a fragment of about a quarter of a whorl of the body chamber ( Fig. 4A ); it has a whorl width of 23 mm, which may correspond to a conch diameter of 60 mm. The weakly depressed whorl profile (ww/wh ~1.25) is rounded-trapezoidal with a flattened venter, a broadly rounded ventrolateral shoulder and a broadly rounded umbilical wall. The whorl overlap zone is very small (IZR ~ 0.10).

The fragment shows the well-preserved shell ornament with 14 spiral ridges on each side from the midventer to the umbilical seam; the ridges are irregularly spaced on the venter but almost equally spaced on the ventrolateral margin and umbilical wall. The growth lines, which extend with a deep, rounded V-shaped sinus across the venter, are much finer than the spiral ridges. They are occasionally strengthened to form a conspicuous granulation; at the crossing with the spiral ridges, they form slightly elongate spines.

Figures

Fig. 4.Specimens of Rineceras Hyatt, 1893.A. Rineceras sp. 1;specimen MB.C.31293.1 (Ebbighausen & Korn 2004 Coll.) from Gara el Itima N; ventral and lateral views, and whorl profile. B. Rineceras sp. 2; specimen PIMUZ 39510 (Karaoui Coll.) from south-east of Rissani; lateral and ventral views. Scale bar units= 1 mm.