Passendorferia (Enayites) cf. rozaki Meléndez, 1989

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 : 521

Passendorferia (Enayites) cf. rozaki Meléndez, 1989 ( Fig. 7F)

MATERIAL EXAMINED. — MI4N 8c/1.

STRATIGRAPHIC DISTRIBUTION. — The specimen has been collected in bed 8d top of section Monte Inici East, which has been assigned with doubt to the Hauffianum Subzone of the Late Oxfordian Bimammatum Zone. The species has been reported from older levels of the Bimammatum Zone, namely the Hypselum Subzone or the lower part of the Bimammatum Subzone ( Atrops & Benest 1986; Meléndez 1989).

DESCRIPTION

Evolute shell with rounded, subcircular whorls. Up to the last quarter of the last whorl the whorl breadth is larger than the whorl height. The ventral area is large and rounded. The ribbing is dense, radiate to slightly prorsiradiate in the second half of the last whorl. Ribs generally bifurcate at the ventrolateral margin and at the upper quarter of the flank towards the mouth; simple ribs are rare. Up to a diameter of at least 53 mm secondary ribs are almost symmetrical with respect to the primary rib from which they spring but they are clearly projected forward in the last part of last whorl. Three oblique constrictions per whorl have been observed: one of them is adorally bounded by a swollen rib and is deeper than the others. The peristome is partly preserved: the venter shows a ridge whereas a broken lappet is visible on the flank after the final constriction. Measurements: see Table 8.

DISCUSSION

The specimen from Monte Inici is rather similar to the holotype of the species but shows a higher number of primary ribs. Furthermore parabolic nodes have not been observed (because of insufficient preservation?). However, Atrops & Benest (1986) have figured two specimens of this species devoid of parabolic nodes. Meléndez (1989) has created the species P. (E.) rozaki on the basis of a specimen that Brochwicz-Lewinski & Rozak (1976) originally included with doubts by in the species P. (E.) gygii . The latter is less evolute and more finely ribbed than P. (E.) rozaki . The separation between these two species may be questionable because of scarce morphological differences. P. (E.) sanpedroi Meléndez, 1989 has a rib density similar to that of the specimen here described but it is less evolute and its secondary ribs are not projected forward.