Your ammonite probably is...

Muensteroceras

Muensteroceras had a 2-lobed suture pattern. Some species were narrow while others were very broad. It had no radial ribs and had a fairly wide umbilicus. Its whorls didn't overlap much. Muensteroceras is from the Mississippian of Michigan, Indiana, and Missouri. This genus is very similar to Goniatites. The main difference is their sutures. Muensteroceras has a deeply sunken lobe on its venter, while Goniatites lacks such a deep sinking.