Description RARE Bostrychoceras elongatum Heteromorph Ammonite Fossil Geological Period: Cretaceous Stage: Lower Campanian (approximately 83.6 to 72.1 million years ago) Location: Tsiribina Basin, Madagascar Formation: Likely part of the Maevarano Formation or associated Campanian marine strata Fossil Type: Ammonite (Heteromorph) Species: Bostrychoceras elongatum This is a rare and beautifully preserved heteromorph ammonite fossil from the genus Bostrychoceras, species elongatum. These ammonites are known for their dramatically uncoiled, turreted, or helical shell morphology — a unique adaptation among the heteromorph ammonites that likely affected buoyancy and orientation in the water column. This specimen originates from the Lower Campanian stage of the Late Cretaceous, discovered in the Tsiribina region of Madagascar. This area is well-known for producing marine fossils from a shallow epicontinental sea environment, with excellent preservation in fine-grained marine sediments. Scientific Details: Family: Nostoceratidae Superfamily: Turrilitoidea Order: Ammonitida Biozone (inferred): Lower Campanian ammonite zones, likely associated with Placenticeras fauna Morphology Features: Strongly helical shell with open-coiling, compressed cross-section, fine to moderate ribbing, and occasional tuberculation or spine bases Depositional Environment: Shallow marine shelf or outer shelf environment, low-energy setting Notable Traits: Bostrychoceras elongatum is a distinctive ammonite used in regional stratigraphy. Its form is an evolutionary departure from the tightly coiled planispiral structure of more common ammonites. Additional Information: All of our Fossils are 100% Genuine Specimens and come with a Certificate of Authenticity. The fossil shown in the photographs is the actual specimen you will receive. Scale Rule Squares / Cube = 1cm. Please refer to the photos for full sizing and detail. This is a carefully chosen and quality-controlled fossil, suitable for collectors, museums, or educational display. This rare ammonite offers a glimpse into the evolutionary diversity of marine life in the Cretaceous seas of ancient Madagascar. An exceptional collector’s specimen with real scientific interest.
