Simulation of one ammonite shell morphotype by another. The fossils below are Schloenbachia varians from the lower Cenomanian (Late Cretaceous) from This Site.
And another with a ventral view from this site
The attached photos are Forresteria alluaudi from the Coniacian (also Late Cretaceous but a few million years younger), the robust, spinose morphotypes are very similar, and at least for me, they would be very hard to differentiate by shell shape alone.
And another with a ventral view from this site

The attached photos are Forresteria alluaudi from the Coniacian (also Late Cretaceous but a few million years younger), the robust, spinose morphotypes are very similar, and at least for me, they would be very hard to differentiate by shell shape alone.