Your ammonite probably is...

Harpoceras

Harpoceras is identified by its sickle-shaped ribs that cover its flanks. It had a sharp keel on its venter. Its shell was involute. This Lower Jurassic ammonite was a good swimmer and had a global distribution.

CC0, https://commons.wikimedia.org/wiki/File:Harpoceras_subplanatum_Mus%C3%A9e_des_Confluences_18_10_2015_1.jpg