Introduction: The Southern Continents as Backgrounds for Mammalian Evolution

Abstract

The isolated southern continents, occupying approximately equivalent latitudinal zones and broadly comparable as living areas, provide an unusual opportunity for a comparative study of mammalian evolution. Each began the Age of Mammals with different mammalian raw material, and each has had a long history of evolution in isolation. This was interrupted by major faunal interchanges only rarely-Africa three times (?), South America once-all other colonization being adventitious. The latest paleontological data strongly supports the contention that each continent received its mammal fauna from the north and not by any direct southern connection. THis is notwithstanding some similarities in the floras and invertebrate faunas of South America and Australia, and fascinating new evidence that Antarctica supported forests in the middle Tertiary. The latest paleomagnetic data on shifting continents confirms that any major sundering occurred in the early Mesozoic, prior to the evolution of mammals.