Biostratigraphy and biogeography of Cretaceous charophytes from South America

Charophytes are non-marine green algae living on the bottom of ancient and Recent lakes and in other non-marine environments. The fossil record of Cre taceous Charophyta considered in this paper includes 56 organ-species, and is the best known of the ancient assemblages in South America. The stratigr aphic distribution of these species is outlined using world-wide chronostra tigraphic units. Three correlated biogeographic patterns are discussed in t he framework of the main geological changes. Early Cretaceous records indic ate a high rate of endemism. In the Aptian some barriers of isolation seem to have been broken or bypassed. Despite many cases of widely distributed s pecies, two separate Late Cretaceous biogeographic provinces are recognized : the Andean Province and the South Atlantic Province. (C) 2000 Academic Pr ess.