The selachians' faunas of the Moroccan phosphate deposits and the KT mass-extinctions

The Cretaceous and Tertiary phosphate deposits of Morocco which have a vertical thickness covering 25 My (Maastrichtian-Lower Lutetian), are well known for their rich fossil archives. The selachians' fish constitute the most abundant and varied vertebrate faunas. Analysis of the dynamics and patterns of extinctions and faunal renewals identified two significant episodes of high rates of extinction. A mass-extinctions event took place at the end of the Maastrichtian (Cretaceous-Tertiary boundary, KT) when more than 95% of species disappeared. The Lower Ypresian witnessed a second, selective, event which appears to have mainly affected sharks. Geochemical analysis may enlighten the environmental changes.