Description. According to Wright (1996), this is a cosmopolitan, rather evolute genus with a rounded or depressed whorl section and a strong siphonal keel that may originate below the ventrolateral rib terminations. The ribs are dense to distant, rounded to sharp, and generally combine simple and bifurcated ribs, the latter swollen at the point of division. Umbilical and ventrolateral tubercles are sometimes present. The suture has broad, massive, and finely indented saddles. Type species Ammonites cristatus Brongniart, 1822. Middle and upper Albian. Europe, South Africa (Zululand), Madagascar, Japan, Texas.
Subgenera. Wright considers two subgenera. The subgenus Dipoloceras sensu stricto has a rounded or depressed whorl section. The umbilical and ventrolateral tubercles are absent or insignificant. The subgenus Rhytidoceras Van Hoepen, 1931, has flattened inner whorls, with distinct umbilical tubercles and weak ventrolateral ones. It combines bifurcated and flexuous ribs with simple and straight ribs. The ribs often bear spiral grooves. Kennedy & Klinger (2023), whose opinion is followed here, make Rhytidoceras a separate genus, which means that genus Dipoloceras has no more subgenera.
A few species. Dipoloceras cristatum (Brongniart, 1822) has a depressed section with strongly rounded flanks, a venter often sunken on either side of the keel, simple or bifurcated ribs, and some hypertrophied ribs that are taller than the others (top drawings, d'Orbigny, 1841). It defines the first zone of Upper Albian of the Anglo-Paris Basin. D. pseudaon Spath, 1931, resembles it but exhibits crenulated ribs. D. fredericksburgense Scott, 1928, has a more rectangular section and less overlapping whorls. The rarely hypertrophied ribs sag a bit before reaching the keel. Kennedy et al. (1999) consider it a variant of D. cristatum because intermediate forms exist. D. bouchardianum (d'Orbigny, 1841) has a moderately compressed elliptical section, with a flattened venter and very rounded ventral shoulders. The numerous ribs bifurcate very low on the flanks and give rise to sigmoid secondary ribs, without hypertrophy, which strengthen on ventrolateral shoulders and stop against the keel, while forming an obtuse ventral chevron (lower drawings, d'Orbigny).
Remarks. The genus is quite common in Folkestone and Wissant, but the Aube has yielded only rare and incomplete specimens (Matrion & Touch, 1997).