VERY RARE Fossil Ammonite SPHENODISCUS LOBATUS – Fox Hills Formation, Maastrichtian, Cretaceous: South Dakota, USA – Genuine & Certified

Description Presenting a VERY RARE and scientifically significant fossil ammonite: Sphenodiscus lobatus, from the Fox Hills Formation, part of the Pierre Shale Group, collected in South Dakota, USA. This beautifully preserved specimen represents a genus that thrived during the final chapter of the Cretaceous Period, in a shallow marine environment just prior to the mass extinction at the K–Pg boundary. Sphenodiscus lobatus is a member of the family Sphenodiscidae, superfamily Desmoceratoidea, and order Ammonitida. It exhibits a streamlined, discoidal shell with flat sides and a keeled venter, characteristics that suggest fast movement through open waters, likely as a nektonic predator or scavenger. Geological & Scientific Details: Scientific Name: Sphenodiscus lobatus Fossil Type: Ammonite (Placenticeratid Morphology) Geological Period: Cretaceous Stage: Maastrichtian (approx. 72–66 million years ago) Formation: Fox Hills Formation (Pierre Shale Group) Location Found: South Dakota, United States Order: Ammonitida Superfamily: Desmoceratoidea Family: Sphenodiscidae Morphological Features: Involute, discoidal shell with strong ventral keel, smooth to weakly ribbed flanks Depositional Environment: Shallow marine – Western Interior Seaway Sphenodiscus lobatus is a noteworthy ammonite species due to its abundance in uppermost Cretaceous marine deposits and its distinct shape, making it highly identifiable in the fossil record. It plays an important role in biostratigraphy of the Late Cretaceous and is often used to correlate marine sequences across North America. All of our Fossils are 100% Genuine Specimens & come with a Certificate of Authenticity. Please Note: Scale Rule Squares / Cube = 1cm – full sizing is shown in the photo The fossil pictured is the exact specimen you will receive, professionally selected for its detail, preservation, and scientific significance This rare ammonite fossil is a perfect addition to any fossil collection or educational exhibit, offering a glimpse into the dynamic marine ecosystems of the Cretaceous seas.