An unexpected vertebrate fossil assemblage on Mallorca (Balearic Islands, Western Mediterranean Sea).

Résumé En

Cave sediments occasionally incorporate the remains of vertebrates than can fossilize, becoming important sources for the knowledge of past faunas. The fossil breccia can even survive the caves where originated and provide information about faunas dated to million years ago. The discovery of Na Burguesa-1 site in Mallorca (Balearic Islands) has provided an unexpected vertebrate fossil assemblage. It corresponds to ancient cave sediments. Nowadays the primordial cavity has been totally eroded and only is preserved the infill sediment. This karstic sediment is composed by sharp pebbles of limestone embedded in a matrix of red-brown silts strongly cemented by calcite. Inside it appear layers with abundant microvertebrate remains, bioaccumulated by raptor birds. Through a long and slow preparation with acetic acid has been possible to recover thousands of disarticulated bones. Terrestrial mammals are the best-represented group, which includes Soricinae, Cricetinae, Muridae, Gliridae, Leporidae and Bovidae specimens. There is also a good herpetological record (4 Anura and 13 Squamata), mainly identifiable to the family level. Instead, birds are the worst represented group. Some of these taxa represent the ancestors of the early Pliocene fauna from Caló den Rafelino (Mallorca). Some others may be related with their late Miocene mainland relatives. The paleontological site of Na Burguesa-1 is attributed to a basal Pliocene, supporting the hypothesis of colonization during the Messinian Salinity Crisis (MSC) due to the great drawdown of the Mediterranean Sea level. After the subsequent flooding of the Mediterranean basin, this paleocommunity remained isolated, evolving in insularity conditions along 5.35 My. Some extinction episodes took place during the Pliocene and only a few species of terrestrial vertebrates (Alytes muletensis, Podarcis lilfordi, Nesiotites hidalgoi, Hypnomys morpheus and Myotragus balearicus) survived on Mallorca until the arrival of the first humans sometime before