| Measurements | D mm | H/D | T/D | O/D | H/T |
|---|---|---|---|---|---|
| Holotype | 57 | 0.44 | ? | 0.26 | ? |
| Spath 1925 pl.X fig.1 | 64 | 0.42 | 0.25 | 0.30? | 1.68 |
| CP-711 | 66.7 | 0.47 | 0.28 | 0.25 | 1.71 |
| Age | Origin |
|---|---|
|
Bed F (sandy limestone) A. intermedius zone Middle Albian |
Courcelles quarry Commune of Clérey Aube, France |
Description. Ammonite with an unprepared aperture, in a gray limestone with a black test showing the sutures. The whorls, 60% covered, have a tall trapezoidal section, with flat, parallel flanks at the base, then becoming slightly convex and converging towards a flat venter with angular shoulders. The profile is that of a compressed Hoplites dentatus. The umbilicus wall, sloping at 50°, rounds towards the flank. It bears 16 proverse and elongated bullae. Each bulla gives two moderatly prominent, flexuous ribs, already quite distinct in the umbilicus. They have a steeper posterior slope and curve forward at the top of flanks. They end by flattening out, without forming a distinct ventral groove, very close to the siphonal line at the beginning of last whorl, and then on the ventrolateral shoulders at the end of the spiral. There are approximately 50 ribs with alternating terminations, forming a 45° angle with the siphonal line. The first lateral lobe L1 is wide, deep and symmetrical, with a trifid termination.
Remarks. An individual similar to that of Young et al. (2010, pl. 31, fig. 1a-b). The species derives from H. dentatus by its ribs that become less prominent, with attenuated external terminations, and a flattened venter. It defines a Middle Albian zone between the dentatus and niobe zones. It typically has about forty ribs and an O/D ratio around 0.25. Some other species of Spath (1925) have been reclassified as variants (Amédro et al., 2014). A. praecox is a robust variant with stronger ribs. A. mantelli is a gracile form with finer, denser ribs, and it is slightly more involute (O/D = 0.21). Finally, A. evolutus has the same ribbing as A. intermedius, but more numerous ribs (45+) and a more open umbilicus (O/D = 0.32). CP-711, with its rather fine ribs, tends towards A. mantelli.