Description. According to Wright (1996), this genus has a compressed subrectangular to depressed trapezoidal whorl section, with prominent ribs arising in pairs from strong umbilical bullae and interrupted on venter. The rib terminations are often thickened or raised and form ventrolateral tubercles. They are opposite or alternate on both sides of the siphonal line. In some species, the ribs are lautiform (looped).
Subgenus Isohoplites Casey, 1954. It has more or less compressed whorls and interrupted ribs on venter, with opposite ends. The ribs then tend to cross venter (Amédro, 1984). Sometimes they are alternate at first, then shift to form opposite ends and finally cross venter, as in specimen no. 77-583 from the Ricordeau collection at the Auxerre Museum. This subgenus has only one species, Hoplites (Isohoplites) steinmanni (Jacob, 1907), which defines a Lower Albian ammonite zone. It is found in England, France, Switzerland, Poland, Svalbard, and Transcaspia. Russian authors such as Saveliev (1992) classify it as a Pseudosonneratia, but this genus had already disappeared by the time the true Isohoplites appeared. The top image shows a specimen from Aube (Amédro et al., 2014).
Subgenus Hoplites sensu stricto. Type species Ammonites dentatus J. Sowerby, 1821. The ribs are interrupted on venter, giving the impression of a sulcus. In fact, the venter is rarely concave if one crosses it via an intercostal space. This subgenus includes four main, highly variable species. H. (H.) benettianus (J. de C. Sowerby, 1826) has a narrow, V-shaped ventral sulcus, with rib terminations often slightly interlocked: if one follows the siphonal line with the tip of a pencil, the tip zigzags. This species defines the ammonite zone after that of H. (I.) steinmanni and includes the Upper Lower Albian (pseudolyelli subzone) and the Lower Middle Albian (lyelli subzone). H. (H.) dentatus (J. Sowerby, 1821) defines the next zone of Middle Albian. It has a wider, straight, U-shaped sulcus (bottom image, Amédro et al., 2014). The other two species are from the upper part of dentatus zone. They also have a U-shaped groove, but their costal terminations are higher and can form spatulae: H. (H.) rudis Parona & Bonarelli, 1897, has ribs folded forward on the outer third of the flanks, while H. (H.) canavarii Parona & Bonarelli, 1897, has lautiform ribs.
Several species are considered to be variants of these four main taxa, see Amédro (1992), Courville & Lebrun (2010), and Amédro et al. (2014).