How, when and where from of the Abruzzo-Apulian paleofauna.

On-shore and off-shore geological investigations in the Abruzzo-Apulian area and Adriatic Sea detected the existence of a structural high between Dalmatia and the Gargano Peninsula, where now are the Tremiti Islands, from the Late Oligocene to the Langhian. The major global sea-level fall that occurred around 29–30 Ma caused the generalized surfacing of this structure across the Adriatic. The isthmus thus constituted a landbridge, either in the form of stripe of land or of a chain of islands. The structural high likely gave rise to an archipelago of gradually shrinking islands as the sea level turned growing at the transition to the Early Miocene. The isthmus definitively sank at the end of the Langhian, i.e. around 14.8 Ma, isolating the Abruzzo–Apulian area for the next 7 million years. Dalmatia and the Gargano were connected again during the Messinian sea lowstand. Thereafter, as the sea level gradually grew once more, the Abruzzo–Apulian area was isolated again and then finally sank at the very end of the Messinian. Although of course sweepstake colonization can be hypothesized to explain the arrival of the taxa that formed the Abruzzo-Apulian’s unique faunal community, the newly available geological information offers an alternative (and far more parsimonious) way of immigration and chronological constraint to its occurrence. In fact, the primitive traits of the Abruzzo–Apulian ungulates and giant insectivores seem perfectly in line with an early colonization of the area.