Carlos Alberto Menendez


From the interpretation of distribution and characters of the present flora arise the following conclusions: The relation of cool-temperate flora of Argentina with other zones geographically discontinuous of the southern hemisphere, is largely illustrated by numerous examples. The distribution, more or les, balanced, of some elements exclusive of the southern hemisphere would suggest a common and equidistant center of origin, and could well be the Antartic continent. The greater abundance of species in the Newzelandic zone of the genera common with South America should indicate a center of dispersion in New Zealand with spread through Antarctica. The primitive character of many tropical plants with clear dominance and frequency in South America suggests an important center of radial dispersion in this zone.
After the interpretation of distribution and characters of the present flora has been made an analysis of the Tertiary palaeobotanical records in South America. In the Tertiary record of fossil plants from Argentina it is possible to distinguish two main floral types: cool-temperate and tropical or subtropical. Throughout the Tertiary in the equatorial zone of South America the tropical floras were dominanting. During the Paleocene-early Eocene took place the maximum southwards-advance of the tropical flora. In the late Eocene and early Oligocene began the northwards-retreat of the warm floristic elements and the parallel advance of the cool-temperate floristic elernents. The character and latitudinal distribution of the Pliocene floras in South America are very similar to those of the actual floras with some differences which mostly ocurred by influence of the orogenic activity.

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