Euhoplites truncatus Spath, 1925

Measurements	D mm	H/D	T/D	O/D	H/T
CP-569 Prins	38.8	0.43	0.42	0.26	1.02
Holotype	60	0.46	0.38	0.28	1.21
Paratype d'Orbigny	47	0.43	0.39	0.28	1.10
CP-654	48.8	0.48	0.42	0.29	1.13

Age	Origin
Bed VII, Middle Albian moyen	Folkestone, England

Description. First, read the entry for Euhoplites lautus. This pyritic ammonite has a pearly test and whorls with a 60% overlap. Its whorl section is compressed hexagonal at the umbilical tubercles, with flanks converging towards a flat venter, grooved by a U-shaped siphonal canal. The smooth umbilical wall has a long, 40° slope and an edge that gradually transitions to the flank. This edge bears 12 pimple-like tubercles, visible on the inner whorls, located in the lower third of the whorl's height. Each tubercle gives rise to two, sometimes three, proverse lautiform ribs, projecting forward at the top of the flank where they meet on a ventrolateral clavus. At the beginning of last whorl, the clavi are oblique to the siphonal canal, then they become almost parallel to the siphon. The ribs extend slightly beyond their clavus, curving obliquely forward, and sagging on the edge of the canal. There are 22 clavi and 42 ribs. Some are zigzag-shaped, and there are also some intercalary ribs without an umbilical tubercle.

Remarks. Spath defined this species for the Ammonites lautus of d'Orbigny (1841), pl. 64, fig. 4-5 (only). Other specimens can be seen in Hadland (2018) and on Jim Craig's website. This taxon is considered by Amédro (1992) to be a thicker variant of E. lautus (see the entry for the latter with a table of variants). The changes that occur with increasing thickness are the same as in Hoplites benettianus and dentatus: the umbilical wall rises, pushing the umbilical tubercles higher on the flanks. These tubercles, as well as the ribs, become stronger and fewer in number. Two other differences from E. lautus can be noted: the tubercles are rounded pimples, instead of being distinctly radially pinched, and the siphonal canal is a bit wider.