6.8" Heteromorph Ammonite (Audouliceras) Fossil - Volga River, Russia
There is some restoration on the ammonite, about 10-15% This is typical for most Audiloceras ammonites sold from this region.
Most ammonites are homomorphs meaning that they retain their spiral shell shape throughout growth. Heteromorph (different shaped) ammonites developed during the late jurassic and have uncoiled shells. It's hard to imagine how this shape would have given them a evolutionary advantage as it would have hindered fast movement.