Goniatitida

Goniatitida is an extinct order of ammonoid cephalopods that lived from the Devonian period to the Permian period. They are characterized by their generally simple, coiled shells with suture lines that are typically goniatitic, meaning they have lobes and saddles that are angular and pointed rather than broadly curved. The shells of goniatitids are often involute, with later whorls completely or partially covering earlier ones. They possessed a siphuncle, a tube that ran through the shell chambers, which was used to control buoyancy by regulating the amount of gas or liquid within.

Fossil evidence indicates that goniatitids inhabited a wide range of marine environments across the globe. Their shells are relatively common in Paleozoic marine sedimentary rocks, making them valuable index fossils for biostratigraphy, helping geologists to date rock layers. The diversity of goniatitid forms and their evolutionary lineages are well-studied, providing insights into ammonoid paleobiology and the history of marine life during the Paleozoic. Their extinction at the end of the Permian period coincided with the largest mass extinction event in Earth's history, the Permian-Triassic extinction.