Origin of the Elements of the endemic "Terre Rosse" fauna (Gargano, South eastern Italy)

The attention of the scientific community has recently been addressed on various aspects of the Messinian endemic vertebrates from the foreland sector of the Abruzzo - Apulian paleobioprovince: several new papers dealing with ruminants, glirids, insectivores, cricetids, as well as with biochronological, palaeographic and biogeographic aspects have been published in the last ten years. New fossils finds enriched the taxonomic composition of the Gargano endemic fauna: a new Cricetodontinae genus, a new Murinae genus representing the direct ancestor of the endemic murid Mikrotia, and a new species of primitive giant moonrat Deinogalerix. The recently published taxonomic description of the smaller moonrat Apulogalerix also contributed to a better knowledge of the endemic Gargano fauna. Although these new data and contributions brought substantial improvement to the taxonomy of the fauna and to the ecology of the moonrats, the debate on the origin and age of dispersal of most of the faunal elements is still open. In this contribution we present some of the open problems regarding the origin of several of the elements of the “Terre Rosse” fauna. The study of the small moonrat Apulogalerix has shown that its most likely continental ancestor should be found in Parasorex socialis – ibericus. Such philogenetic relationship constrains the age of its dispersal on the insular realm to the Late Vallesian (MN9-10). This is in partial contradiction with paleogeographic reconstruction based on geological data, which suggest that the time slice MN6-MN11 is the least favourable time interval for the dispersal of the taxa on the insular domain. The study in progress of the new genus of Cricetodontinae shows that this form is not clearly related to any of the known continental genera. The features of this new genus, however, are more compatible with a possible derivation from some Cricetodon-like genus. This affinity suggests an age of dispersal of Early Miocene-early Middle Miocene (MN4-5) or older and implies that the “Terre Rosse” fauna is the result of different dispersals event scattered in different time slices. A still open problem is represented by the Crocidosoricinae shrew named as Lartetium in the literature. Indeed, the absence of residual a3, a character considered as diagnostic of the genus, renders the generic attribution very problematic and would require further investigations. The new discovered Murinae genus shares a number of synapormophies with Mikrotia genus. Its description should be completed, however, by the comparison with the smallest and most primitive Mikrotia from the Terre Rosse. The question of the continental ancestor of this taxon is still unresolved and the preliminary comparisons with European Murinae taxa unfortunately did not shed light on its philogenetic relationship and therefore this matter deserves much more efforts. The Apodemus species from the “Terre Rosse” has never been studied in details. Preliminary observations pointed out that this form shows similarities with late Turolian-Ruscinian Apodemus forms from continental Europe. A more detailed analysis, currently under development, seems to confirm this interpretation and, therefore, permits to exclude a derivation of this form from more primitive Apodemus species (referred to as genus “Parapodemus” by several authors).