Post-triassic nautiloid genera

Studies on tetrabranchiate cephalopods have added much data to our understanding of the patterns and modes of evolution as displayed by fossil animals. Few invertebrate phyla show such marked periods of expansion in evolutionary intensity contrasted with periods of extreme contraction to the point of near extinction. The generalized evolutionary history of the ammonoids with periods of near extinction at the end of the Paleozoic and again at the end of the Triassic, and their final extinction at the end of the Cretaceous is well known. Among the nautiloid cephalopods a similar evolutionary history exists but with some important differences <...>