Goniatites are an extinct group of marine cephalopods that lived during the Paleozoic era, specifically from the late Devonian to the late Permian periods. They are characterized by their coiled, chambered shells, which often display intricate patterns and suture lines. These creatures are part of the larger class of cephalopods, which also includes modern squids and octopuses. Goniatites are important to paleontology because their fossilized remains are used as index fossils, helping scientists date the rocks in which they are found. Their diverse forms and widespread distribution make them valuable for understanding ancient marine environments and the evolutionary history of ammonoids, a related group of cephalopods.