| Measurements | D mm | H/D | T/D | O/D | H/T |
|---|---|---|---|---|---|
| 658 Prins | 45.7 | 0.44 | 0.55 | 0.30 | 0.80 |
| Paratype Spath | 75(66) | 0.45 | 0.40 | 0.26 | 1.12 |
| Holotype Spath | 103 | 0.44 | 0.50 | 0.30 | 0.88 |
| Age | Origin |
|---|---|
|
Phosphatic level P5 cristatum zone Base of Upper Albian |
Wissant Pas-de-Calais France |
Description. Black phosphate ammonite with a pearly test and whorls 40% covered. The aperture is hidden by a large phosphate plug, the removal of which is always risky on specimens from Wissant. Hexagonal whorl section, with venter grooved by a thin, U-shaped siphonal canal, sinuous at the end (malformation?). The smooth umbilical wall slopes at 40°, transitioning to the flank without a clear boundary. Its edge bears nine increasingly prominent button-like tubercles, visible on the inner whorls and located halfway up the cross-section. The canal is bordered by 18 ventrolateral tubercles. At the beginning of the last whorl, these are low and elongated, forming a 50° angle with the canal. They then transition into clavi parallel to the siphon, becoming increasingly prominent and slightly inclined outwards. In the first half of the last whorl, there are 24 thin, closely spaced ribs, lautiform or zigzagging, convex but not projecting forward. Each umbilical tubercle gives rise to 3 ribs. Two successive tubercles are separated by 2 or 3 ribs originating at the same height. The ribs generally end in groups of 3 on a ventrolateral tubercle and disappear on the last half-whorl.
Remarks. One of Spath's specimens is particularly similar (Spath, 1930, pl. 30, fig. 12); see also a fine specimen from bed VIII of Folkestone on Jim Craig's website. According to Amédro (1992), the species belongs to the series of E. ochetonotus (see the genus entry), which regroups Euhoplites with a U-shaped canal and fine, dense ribs, not projecting forward near venter. E. trapezoidalis is distinguished from E. ochetonotus by stronger tubercles and a thicker section: H/T = 0.88–1.12 vs 1.45–1.65.