Geography of Phocid Evolution

摘要: Ray, C. E. (Department of Paleobiology, Smithsonian Institution, Washington, D. 20560) 1976. Geography Phocid Evolution. Syst. Zool. 25:391-406.-Phocid distribution suggests origin in and primary radiation from the North Atlantic-Paratethyan region. Phocines monachines are equally old groups, known first lower middle Miocene Calvert Formation. dominated Paratethys semi-isolation. Both groups dispersed freely around margins Atlantic Pliocene time. entered Pacific, probably north, time, have modernized radiated latest Cenozoic exclusively cold waters northern hemisphere. Monachine receded southward during they spread into both southern hemisphere, where empty Antarctic, Pacific via American seaway. At least four forces acting independently over past decade or so combine now to make a fresh look at geography marine mammals its interplay with their systematics rewarding: 1. ITe revitalization paleogeography resulting new dynamism concepts crustal evolution. Plate tectonics sea floor spreading general theme geology today, but most us United States who finished our formal schooling as little 15 years ago were reared scholastically on supposedly solid foundation stable continents, dutiful if not derisive bow toward continental drift, followed by quick dismissal. The impact colliding continents is being felt throughout geology. 2. development cosmopolitan time frame for Era, through long distance correlation planktonic foraminifera nannoplankton, magnetic radiometric techniques. integration these lines evidence, increasingly rigorous application stratigraphic principles, has provided comprehensive working hypothesis against which fit patterns mammal relationships may be