Your ammonite probably is...
Cheiloceras
Suture: Goniatitic
Cheiloceras was one of the oldest true Goniatites, living in the Upper Devonian. It was rather abundant, but incredibly small. It had very well-defined suture lines.
Image by Dr. René Hoffmann, CC-BY SA 3.0, https://commons.wikimedia.org/wiki/File:Cheiloceras.jpg