Hildaites BUCKMAN, 1921

Sassaroli, Stefano & Venturi, Federico, 2012, Early Toarcian (post-OAE) Hildoceratinae (Ammonitina) fauna from the Marchean Apennines (Italy), Revue de Paléobiologie 31 (1), pp. 85-114 : 95

Genus Hildaites BUCKMAN, 1921

Type species: Hildaites subserpentinus BUCKMAN, 1921 .

Synonyms: Murleyiceras BUCKMAN, 1921; Hildoceratoides BUCKMAN, 1921; Harpohildoceras RE- PIN, 1970, according to HOWARTH (1992) and BÉCAUD (2006).

Amended diagnosis: From evolute to moderately involute shells of various size, which usually show more or less overlap of the whorls. The whorl section may be elliptical, ovaloid, sub-trapezoidal, sub-quadrate or subrectangular. The umbilical edge is rounded; the high or low umbilical wall may be sloping, variably rounded or vertical. The wide or narrow venter may be acute-keeled, tabulate, either bisulcate or tricarinate-bisulcate with raised keel characterized by a sub-triangular section. The ornament shows from fine to strong ribs, which usually are single and sometimes bifurcating, more rarely trifurcating or bundled (fasciculate) forming some reliefs and dimples (sometime with little tubercles or bullae) placed near the umbilical edge. The ribs are more or less fading and also backwards angled (retroverted) near the umbilical edge, but sometimes they start sharply from the umbilical wall; then, they became more or less sinuous and variously projected toward the ventro-lateral edge, taking the typical sinuous, sigmoidal, falcate-falcoid appearance. The suture lines are usually slightly jagged or frilled with spaced lobes; they usually do not intersect each other. The E lobe is sometimes as long as the L lobe, otherwise it is shorter than L lobe. The two umbilical U 2 and U 3 lobes are not much developed, but U 2 is always larger than U 3. The ES saddle commonly is as wide as the double width of saddle LS 1, which on the other hand is wider than the saddle LS 2; they are rarely equal. The hidden internal suture line shows a U 1 lobe, which is shorter and narrower than U 2, or equal. The I lobe is simple, long and narrow.

Remarks: We have improved the HOWARTH (1992) and BÉCAUD’ s (2006) diagnosis, because the finding of until unpublished samples from the Marconessa quarry have enlarged the genus variability.

Occurrence: This genus characterizes the early Toarcian. It shows a considerable biodiversity over the time-span and a wide geographical dispersal, chiefly in the West Tethyan, Submediterranean and Suboreal Provinces.