Gregoryceras ferchaudi Bert, 2004

Cecca, Fabrizio & Savary, Bérengère, 2007, Palaeontological study of Middle Oxfordian- Early Kimmeridgian (Late Jurassic) ammonites from the Rosso Ammonitico of Monte Inici (north-western Sicily, Italy), Geodiversitas 29 (4), pp. 507-548 : 531

Gregoryceras ferchaudi Bert, 2004 ( Fig. 9C)

Gregoryceras ferchaudi Bert, 2004: 72 , 76, pl. 12, figs 2-4, pl. 13, figs 1-5, pl. 14, figs 1, 2, text-fig. 14, synonymy list.

MATERIAL EXAMINED. — MI3 11a/1.

STRATIGRAPHIC DISTRIBUTION. — Interval 11 of Castello Inici section. According to Bert (2004) G. ferchaudi is limited to the Middle Oxfordian Plicatilis Zone, Parandieri Subzone.

DESCRIPTION

Evolute shell with subtrapezoidal whorl section, large and flat umbilical wall. Flanks are almost flat in the last whorl and slightly rounded in the internal whorls. Venter is slightly rounded. Sculpture is characterized by strong rursiradiate ribs, springing, simple or in pairs, from primary ribs which, at their turn, originate from umbilical tubercles or bullae. Ribs are already developed from a diameter of 7 mm. All ribs slightly thicken at the ventrolateral margin and then cross the venter without interruption. No traces of peristome are visible. Due to the lack of any traces of suture line the diameter of the beginning of the body chamber cannot be observed. Measurements: see Table 16.

DISCUSSION

The studied specimen is poorly preserved thus making sculpture details not accurately visible. It shows however strong morphological similarities with one of the specimens figured by Gygi (1977: pl. 2, fig. 2) as “mittlere Variante” of the species G. riazi .