Hypacanthoplites elegans  (Fritel, 1906)

Measurements	D mm	H/D	T/D	O/D	H/T
CP-194	23.1	0.42	0.37	0.31	1.13
Kennedy 2000	50.5	0.46	0.37	0.28	1.24

Age	Origin
Quarry of grey clay schrammeni zone Late Aptian-Basal Albian	Vöhrum Lower Saxony Germany

Description. Small, septate specimen with a pearly test, one side and the aperture still embedded in a black phosphate nodule with a gray cortex, the usual preservation at Vöhrum. Evolute coiling with a whorl overlap of 1/3. Section somewhat compressed, resembling a rectangle with truncated upper corners. The venter on the last quarter of whorl was abraded during the formation of the nodule. The maximum thickness is at the umbilical margin. The umbilicus, rather low and sloping at 70°, transitions to the flanks via a rounded edge. At the beginning of last whorl, the closely spaced, proverse, and flexuous ribs include primaries arising at the umbilical suture and bifurcating on an umbilical bulla, sometimes a bit higher. These primaries also bear tiny lateral and ventrolateral tubercles. They are separated on average by one untuberculate secondary rib arising at mid-flank. On the last half-whorl, there is an alternation of undivided primaries that have lost their lateral tubercle, and shorter intercalaries. A total of 48 ribs cross the venter at right angle.

Remarks. This ammonite differs from its congeners of Vöhrum by its thinner, more numerous, slightly sigmoid ribs, and its small umbilical bullae that quickly disappear on bigger specimens. The number of ribs is highly variable and can reach 70 (Kennedy, 2000). This author considers H. hanovrensis (Collet, 1907) and H. spathi (Dutertre, 1938) as mere variants. This species is found in the jacobi zone (late Aptian) in the Anglo-Paris Basin, in the Alps (Pré-Guittard, Tartonne), and in Germany. At Vöhrum, it extends into the schrammeni zone, which marks the beginning of the German Albian (Mutterlose et al., 2003). We do not know the exact collection level of our specimen, so it could be aptian or albian.