The image shown above is ammonoid mollusk fossil called Acanthoscaphites nodosus (Owen, 1852). This animal fossil dates to the Late Maastrichtian Stage, Cretaceous Period between 144 and 65 million years ago of the Mesozoic Era. It was found Montana, USA.
The fossil was on display in the Evolving Planet section of The Field Museum of Natural History in Chicago Illinois, USA as of August 2020. Accession number is PE3908.
Species named by David Dale Owen, he collected during geological surveys of Wisconsin, Iowa, and Minnesota. Published in 1852 and at that time called Scaphites nodosus. The genus was named by Nowak in 1912.
