Miocene-Pliocene faunal turnover at As-Sahabi (Libya): Ecological restructuring through the Messinian Salinity Crisis

The As-Sahabi fossil site in northeastern Libya is a pivotal site for understanding late Miocene-Pliocene ecological dynamics in North Africa, particularly its biogeographic role linking central and Northern Africa. This study investigates large-mammal fossil assemblages comprising 2841 specimens from the late Miocene Sahabi Formation (units T, U1, U2) and Pliocene Qarat Weddah Formation (unit V) in order to assess (1) whether these stratigraphic units represent a single biological community or distinct communities and (2) Whether mammal faunal turnovers agree with environmental changes that occurred during the late Miocene and Pliocene, including the Messinian Salinity Crisis (MSC). Using coverage-based rarefaction and multivariate analyses, we identify three distinct paleo-communities corresponding to stratigraphic units T, U1/U2 and V. Unit T, dominated by marine mammals (61% Sirenia/Cetacea), reflects shallow marine conditions; units U1/U2 transition to diverse habitats with a dominance of Bovidae and Suidae; and Unit V shifts mainly to fluvial environments in which Hippopotamidae are abundant, suggesting a reduction in the ecological spectrum between the late Miocene and the Pliocene. Such a temporal habitat contraction and taxonomic loss are also documented by beta diversity analyses that reveal nestedness-driven turnover between units. Our findings support the hypothesis that the MSC significantly influenced regional ecosystems, with aridification and hydrological changes likely driving the restructuring of large-mammal communities. These findings highlight As-Sahabi’s importance in documenting the impacts of MSC on peri-Mediterranean biomes, emphasizing faunal and habitat shifts during this critical period of Earth’s history.