Abstract:
Using the Paleobiology Database, the distribution of marine mammal genera was
analyzed across geologic time in an effort to isolate dispersal routes. Measurements of
beta diversity were used to quantify the overlap between different ocean basins at
different points in time. A recently introduced measurement of overlap was analyzed and
found to be highly correlated with traditional methods, although conditions causing a
deviation from this correlation are presented. Overlap is used to test existing marine
mammal dispersal hypotheses. The Strait of Gibraltar was found to play a significant role
in the dispersal of cetaceans and sirenians. Conversely, the Central American Seaway
was found to play only a minor role in the high overlap values between the Atlantic and
Pacific oceans seen in extant taxa. Instead, it is asserted that this overlap is largely the
result of Arctic dispersal pathways in the Quaternary.
