Updating the Europe-Africa small mammal exchange during the late Messinian

Aim: The Messinian salinity crisis (MSC) was an extraordinary geological event that affected the whole Mediterranean region as well as the global marine circulation between 5.97 and c. 5.33 Ma. One of its most direct effects was the emersion of land masses and the subsequent establishment of land bridges that led to common terrestrial faunal exchanges. However, the details of the onset of these exchanges have been a matter of controversy. New findings from southern Iberia of small mammal remains with African similarities have enabled us to review the Messinian faunal exchanges in the Mediterranean region. Location: Mediterranean region. Methods: Small mammal remains with African similarities from two new southern Iberian sites were studied. The small mammal associations of eight Miocene-Pliocene North African sites were also reviewed. Results: Two taxa with African similarities were identified at the Iberian study sites: Debruijnimys almenarensis and a Ruscinomys-like form (cf. Ruscinomys) with a strong spur in the lingual lobe of the anterocone in the M¹, a feature observed in North African Ruscinomys and eastern Mediterranean Byzantinia. The taxonomic status of some North African species and/or genera, such as Castillomys, Occitanomys and Prolagus, should be revised according to the new phylogenetic relationships established in European faunas. Main conclusions: Two hypotheses can be proposed for the origin of the African Ruscinomys: (1) among the Iberian Ruscinomys or (2) from the eastern Mediterranean Byzantinia. Our data, currently from only a few, albeit significant, taxa, tend to support an Iberian origin. The discussion presented in this paper suggests an age near the closure of the last Betic Gateway (c. 6.18 Ma) for the first small mammal exchange between Africa and Europe, as well as a single migratory wave of small mammals, filtered by their ecological preferences from this point until the end of the MSC.