Trilobite biodiversity trends in the Devonian of North Africa
Abstract Taking advantage of the exceptional record of Devonian trilobites in North Africa, a new dataset was compiled in order to reveal their long-term evolutionary history leading to their extinction. This dataset comprises 1171 trilobite occurrences from 168 different localities, within 22 consecutive and discrete chronostratigraphic intervals (substage temporal scale), representing 556 species, 179 genera, and 15 families scattered among nine North African basins. The reconstructed palaeobiodiversity trajectories by means of various biodiversity estimators of taxonomic richness are consistent and highlight a progressive and continuous diversification throughout the Early Devonian to reach a maximum of diversity at the end of the Emsian. Most families encountered in North Africa contribute to this increase of diversity. This regional diversification shows the same trends as the global one. Thereafter, the trilobite diversity began to decline due to extinction rates higher than origination rates during the Eifelian (Middle Devonian). From the middle Givetian to the late Frasnian, the trilobite diversity remained low. After this major decline, and the Frasnian events, a faunal change occurred, especially in phacopid and proetid trilobites, which were the only two families crossing the Frasnian/Famennian boundary. Indeed, the Kellwasser Event impacted an already impoverished diversity leading to a major faunal renewal associated with quick taxonomic changes at the genus level. A larger proportion of deeper water and reduced-eye/blind trilobites who acted as opportunists characterized the Famennian recovery. Finally, these palaeobiodiversity trends are compared to those of ammonoids from the same area.