Your ammonite probably is...

Hoplites

Hoplites had a narrow, slightly involute shell with a ventral groove. It had very strong radial ribbing, although the suture may be visible. Hoplites lived in the Upper Cretaceous of Europe.

CC0 1.0, https://commons.wikimedia.org/wiki/File:Hoplites_weissi_-_Fossils_in_the_Arppeanum_-_DSC05539.JPG