WAAGENOCERAS

genus of extinct cephalopods (animals related to the modern squid, octopus, and nautilus) found as fossils in Permian marine rocks (from about 286 to 245 million years ago). Waagenoceras has a small, globular shell whose distinctive pattern of sutures between shell chambers is complexly convoluted, aiding in identification. Some species of Waagenoceras serve as excellent guide, or index, fossils for different spans of Permian time.