The conventional limits of the marine biogeographical Sector 4, for the new Checklist of the Italian Fauna

The status of a distinct biogeographical sector for the area of the Strait of Messina has been widely acknowledged in the last two decades. However, clear-cut limits of this sectors have never been formalised. With the understanding that in nature the limits of biogeographical sectors are usually not clear-cut, and for the sake of unequivocally placing occurrences in this sector we have here: (1) summarized the history of the classification of the Strait of Messina as a biogeographical sector, and (2) provided the conventional limits of Sector 4, as far as possible reflecting main ecological traits and recognizable discontinuities with the neighbour sectors