Systematics, biostratigraphy and evolutionary pattern of the Oligo-Miocene marine mammals from the Maltese Islands

An overview of the upper Oligocene-upper Miocene marine sediments outcropping in the Maltese Islands provides a detailed stratigraphical setting of several marine mammal assemblages. The studied fossil material collected within the entire sequence, is now kept in the National Museum of Natural History of Mdina (Malta). Nannoplankton analysis of some selected sections, where mammal remains have been discovered, is also undertaken. The fossil marine mammals, consisting mostly of isolated ear bones and teeth, are referred to cetaceans (both mysticetes and odontocetes), sirenians, and pinnipeds. The cetacean record evidences an evolutionary pattern that agrees with the Oligo-Miocene general trend, characterized by the progressive rarefaction and disappearance of archaic families (squalodontids, waipatiids, and, maybe, mammalodontids), and by the appearance and diversification of the extant families represented within younger strata (kogiids, pontoporiids and ziphiids). Pontoporiids, waipatiids, and tentatively mammalodontids are here reported for the first time in the Mediterranean, while the kogiid record represents the only sure Miocene evidence of this family in the Mediterranean. The geographical distribution of the mammalodontids and the waipatiids, based on the Maltese and extra-Mediterranean records, supports an open communication between the Proto-Mediterranean and the Indo-Pacific during the late Oligocene. Sirenians are represented by several dugongid pachyosteosclerotic rib fragments, collected from upper Oligocene through upper Miocene sediments. Pinnipeds are represented by a femur fragment from the Serravallian, referred to an indeterminate monachine, a phocid subfamily already reported from the Mio-Pliocene of the Mediterranean.