Sinusiidae

Sinusiidae is a family of extinct ammonoids, a diverse group of cephalopods that lived in the ancient oceans. These marine invertebrates are characterized by their coiled shells, which served as protection and a buoyancy mechanism. The family Sinusiidae is distinguished by specific features of its shell coiling and suture patterns, which are the lines where the internal walls of the shell meet the outer wall. These features are crucial for classifying and differentiating fossil ammonoids.

Fossils of Sinusiidae are found in marine sedimentary rocks dating primarily to the Jurassic period. Their geographical distribution suggests they inhabited various marine environments across the globe during this time. Like other ammonoids, Sinusiidae are important index fossils, meaning their presence in rock layers helps geologists determine the age of those rocks. The study of Sinusiidae contributes to our understanding of ammonoid evolution and the paleoecology of Jurassic seas. Their extinction, like that of all ammonoids, occurred at the end of the Cretaceous period, marking the end of a long and successful evolutionary lineage.