Rhaeboceras burkholderi Ammonite Fossil Bearpaw Shale Montana Cretaceous COA Treasure County Late Campanian Marine Fossil

Description

Genuine Rhaeboceras burkholderi Ammonite Fossil

This listing is for a genuine Rhaeboceras burkholderi ammonite fossil from the Bearpaw Shale of Treasure County, Montana, USA. Dating from the Late Campanian Stage of the Upper Cretaceous, this fossil represents a fascinating marine cephalopod from the ancient seas that once covered much of western North America.

Rhaeboceras burkholderi is a highly collectible Cretaceous ammonite species, especially valued for its connection to the fossil-rich marine deposits of Montana. This specimen is a carefully chosen piece, and the photograph shows the actual fossil you will receive. Full sizing can be seen in the photo.

Geology, Age and Location

This ammonite comes from the Bearpaw Shale, a well-known Upper Cretaceous marine formation exposed across parts of Montana and neighbouring regions of the northern Great Plains. The Bearpaw Shale was deposited within the Western Interior Seaway, a vast inland sea that stretched from the Arctic region down through the centre of North America during the Cretaceous Period.

The fossil is Late Campanian in age, placing it within the later part of the Cretaceous, approximately 76 to 72 million years old. This was a time when the Western Interior Seaway supported a rich and varied marine ecosystem. Ammonites, inoceramid bivalves, gastropods, fish, sharks, marine reptiles, and other sea creatures lived in these waters while dinosaurs inhabited the coastal plains and nearby landmasses.

Treasure County, Montana is part of a region famous for Upper Cretaceous fossils preserved in shale, mudstone, and concretionary deposits. The Bearpaw Shale records offshore marine conditions, where fine sediment settled on the seafloor and helped preserve shells and other remains. Many ammonites from this formation are found within hard concretions, which can protect their delicate shell structure over millions of years.

Fossil Type and Species Details

Rhaeboceras burkholderi was an ammonite, an extinct marine mollusc related to modern squid, cuttlefish, octopus, and nautilus. Like other ammonites, it had a chambered shell used for buoyancy control, with the living animal occupying the final body chamber. These animals were active components of Cretaceous marine food webs and are among the most recognisable fossils from ancient seas.

The genus Rhaeboceras is known for its coiled ammonite shell form and belongs within the broader ammonoid group of cephalopods. Rhaeboceras burkholderi was formally named by W. A. Cobban in 1987, and material of this species is associated with Campanian marine shale deposits of Montana. Scientific classification places it within Phylum Mollusca, Class Cephalopoda, Subclass Ammonoidea, and Family Scaphitidae.

This species is especially interesting because Rhaeboceras represents part of the diverse Late Cretaceous ammonite fauna of the Western Interior Seaway. Its shell would originally have been divided into internal chambers, with complex sutures marking the junctions between chamber walls and the outer shell. These suture patterns are a key feature used in ammonite identification and add strong scientific interest to specimens from this group.

Bearpaw Shale Marine Environment

The Bearpaw Shale formed in a relatively quiet marine setting as the Western Interior Seaway changed through time. Fine-grained mud accumulated on the seafloor, preserving fossils from animals that lived in the water column and on the seabed. Ammonites such as Rhaeboceras burkholderi would have lived in this marine environment alongside other Late Cretaceous invertebrates and vertebrates.

Fossils from the Bearpaw Shale are particularly popular with collectors because they capture the rich marine life of North America during the final part of the Age of Dinosaurs. Some ammonites from the formation are known for attractive preservation, natural shell detail, visible sutures, and occasional iridescent shell material depending on the individual specimen and preservation conditions.

Collectible Cretaceous Ammonite Fossil

This Rhaeboceras burkholderi ammonite is an excellent fossil for collectors interested in Cretaceous marine life, ammonite evolution, Montana fossils, or the Western Interior Seaway. Its named species, geological formation, age, and locality make it a desirable addition to a fossil collection, educational display, natural history cabinet, or geology-themed gift selection.

The fossil is a genuine specimen and includes a Certificate of Authenticity lifetime guarantee generic card. The photo shows the actual fossil you will receive, making this a carefully selected and accurately represented collector’s piece from the Upper Cretaceous Bearpaw Shale of Montana.