Your ammonite probably is...

Goodhalites

Goodhallites had a narrow profile. It was loosely coiled and had a wide umbilicus. It had tubercles along the umbilicus that grew stronger with age. Its flanks were packed with fine, weak radial ribs. It had a distinct ventral keel. Its suture pattern had sharp indents. The related genus Mortoniceras had strong radial ribs and sometimes no keel. It also had a more rounded suture. Goodhallites lived in the Lower Cretaceous and is sometimes placed in the related genus Prohysteroceras.