Ammonite

Rouchadzeites sp.

• Cretaceous
• Giraudi Zone?
• Alpes-de-Haute-Provence, France

Size: 8 cm across

This is an unusual heteromorph ammonite with a very small turret followed by loosely coiled and rapidly expanding planispiral whorls. It was originally labeled "Colchidites ellipticus". However, it seems Colchidites is now an invalid genus, with its species distributed between the genera Heteroceras and Martelites. The distinction between these two is in the presence of "a planispiral stage between helix and shaft/hook" in the latter (Delanoy 1997, Raissosadat 2018), which is consistent with this specimen.

Addendum: Cyril Baudouin has identified this specimen as closer to something like Rouchadzeites lazarini (Delanoy & Bert 2006).