Picture of aragonite ammonite shell fossil of a Sphenodiscus sp. The creature existed the late Cretaceous Period Upper Maastrichtian stage. Fossil was found in Fox Hills Formation of South Dakota USA. Specimen was on display at the Muséum National D'Histoire Naturelle Minéralogie et Géologie in Paris France (August 2016).
Learn more here:
http://www.mnhn.fr/fr/visitez/lieux/galerie-mineralogie-geologie
