Polyptychoceras is an extinct genus of ammonites from the Late Cretaceous of Japan. All these ammonites are found in Hokkaido island in Yubari prefecture, Obira or Mikasa.
These are heteromorph ammonites, rare and hard to find.
All these fossils are found from paleontologist Gianpaolo Di Silvestro.
 
Polyptychoceras yubarense
Late Cretaceous
Upper Yezo Group
Obira- Rumoi-
Hokkaido Japan