DETERMINING FACTORS IN THE TERMINAL EXTINCTION OF CRETACEOUS AMMONOIDS

Ammonoids survived several of the major crises on Earth over the 300 Myr of their existence, but their terminal extinction around the Cretaceous/Paleogene (K/Pg) boundary has remained unexplained. A database was created which combines morphometric, stratigraphic and palaeobiogeographic data in 524 datasets for 179 Late Cretaceous species of Phylloceratina, Ammonitina, planispiral Lytoceratina and heteromorphs. Long-term trends in the evolution of Late Cretaceous ammonoids, their hatchlings and their palaeobiogeographic distribution can be compared to those of the very last ammonoid species prior to their terminal extinction. Factors like dispersal potential, latitudinal distribution, hatchling size, fertility, evolution rates and pre-adaptions are discussed at global scale. It can be identified which of these factors supported longer survival, although factors vary between the four orders. The evaluation of the database allows an approach in the understanding of the terminal extinction of these formerly dominant elements of marine ecosystems.