Fossil whale barnacles from the lower Pleistocene of Sicily shed light on the coeval Mediterranean cetacean fauna

[摘要] We report on three shells of whale barnacle (Cirripedia: Coronulidae) collected from Pleistocene shallow-marine deposits exposed at Cinisi (northwestern Sicily, southern Italy). These specimens are identified as belonging to the extinct species Coronula bifida Bronn , 1831. Calcareous nannoplankton analysis of the sediment hosting the coronulid remains places the time of deposition between 1.93 and 1.71 Ma ( i.e. , at the Gelasian-Calabrian transition), an interval during which another deposit rich in whale barnacles exposed in southeastern Apulia (southern Italy) formed. Since Coronula Lamarck , 1802, is currently found inhabiting the skin of humpback whales [Cetacea: Balaenopteridae: Megaptera novaeangliae ( Borowski , 1781)], and considering that the detachment of extant coronulids from their hosts' skin has been mainly observed in occurrence of cetacean breeding/calving areas, the material here studied supports the existence of a baleen whale migration route between the central Mediterranean Sea (the putative reproductive ground) and the North Atlantic (the putative feeding ground) around 1.8 Ma, when several portions of present-day southern Italy were still submerged. The early Pleistocene utilization of the epeiric seas of southern Italy as breeding/calving areas by migrating mysticetes appears to be linked to the severe climatic degradation that has been recognized at the Gelasian-Calabrian transition and that is marked in the fossil record of the Mediterranean Basin by the appearance of "northern guests" such as Arctica islandica ( Linnaeus , 1767) (Bivalvia: Veneroida). The subsequent abandonment of the Mediterranean Sea by most species of mysticetes is likely to have resulted from the progressive emergence of shallow-water coastal environments that occurred in Calabrian and Middle Pleistocene times.

[学科分类] 地质学