Processes of island colonization by Oligo-Miocene land mammals in the central Mediterranean: new data from Scontrone (Abruzzo, Central Italy) and Gargano (Apulia, Southern Italy)

The discovery of Deinogalerix freudenthali BUTLER 1980 at Scontrone, in the southeastern part of central Italy, revives interest in the Late Neogene colonisations of the Abruzzo–Apulian area, which includes also the renowned fossiliferous sites of the Gargano Peninsula. New geological evidence indicates that (1) the Scontrone fossiliferous beds are shallow-marine to lagoonal carbonates from the Early Tortonian, not older than zone N16 of the planktonic foraminiferal biostratigraphy; (2) a major global sea-level fall around 29–30 Ma caused the generalized surfacing of a landbridge connecting Dalmatia with the Gargano Peninsula; (3) 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. The two areas were reconnected during the Messinian sea low-stand; then the Abruzzo–Apulian area was isolated again and finally sank at the very end of the Messinian. The Oligocene–Langhian landbridge was crossed by the ancestors of two bizarre mammalian taxa, i.e., the artiodactyl Hoplitomeryx and the giant insectivore Deinogalerix. The subsequent isolation of the Abruzzo–Apulian area however induced these colonizers to endemize. The diversification of the insectivores and of the hoplitomerycids indicates that the Abruzzo–Apulian paleobioprovince was both vast and varied, but the low overall biodiversity of the fauna as well as the homeomorphy of the different artidactyls indicate that the route had had a strong filtering effect on the incomers. The new geological and paleontological information from Scontrone suggests a need to rethink both the systematics of the hoplitomericids and the origin of Deinogalerix and, together with the data from the Gargano Peninsula, sheds thoroughly new light on the Oligo–Miocene processes of island colonization by land mammals in the central Mediterranean.