Pseudophylloceras

Pseudophylloceras is an extinct genus of ammonites, cephalopod mollusks that lived during the Jurassic and Cretaceous periods. Ammonites, in general, are characterized by their coiled, chambered shells. The genus Pseudophylloceras belongs to the order Phylloceratida, a group known for their generally smooth, globose shells and distinctive suture patterns.

Fossils of Pseudophylloceras are found in marine sedimentary rocks worldwide, indicating a broad paleogeographic distribution. These ammonites are often preserved as internal molds or as original shell material, which can sometimes exhibit iridescent nacre. Their shells typically display a lenticular or compressed discoidal shape, with a relatively smooth surface, though some species may show faint constrictions or ribbing.

The internal structure of the Pseudophylloceras shell, like other ammonites, was divided into chambers by septa. The animal lived in the outermost chamber, the body chamber, while the preceding chambers were filled with gas and liquid, allowing for buoyancy control. The suture lines, where the septa meet the shell wall, are a key characteristic for ammonite classification. In Pseudophylloceras, these sutures are typically complex and deeply incised, a hallmark of the Phylloceratida.

The precise ecological role of Pseudophylloceras is not fully understood, but like most ammonites, they were likely nektonic or planktonic, swimming or drifting in ancient seas. Their diet probably consisted of small marine organisms. The extinction of Pseudophylloceras, along with all other ammonites, occurred at the end of the Cretaceous period, likely due to a combination of environmental changes and catastrophic events.