Land-mass migrations of late Cretaceous mammals

We have already noted the Cretaceous period as the geological period ranging approximately from 146 million years ago to 65 million years ago. During this period the geographical distrib- ution of Earth's land masses was apparently substantially differ- ent than it is today. Some 375 million years ago, two large supercontinent called Laurasia and Gondwana comprised most or all of the present continental land masses, Laurasia in the north and Gondwana in the south. These two supercontinents merged into the single supercontinent Pangaea about 250 million years ago, and subsequent fragmentation of Pangaea began about 180 million years ago and the fragmentation eventually produced the continental land masses we know today. During this fragmentation there existed the second phase of Gondwana, incorporating what is now South America, Africa, Antarctica, Australia, and India. This historical picture, which is the present general consensus, is the result of a large number of geological and paleobiological studies, and in paleobiology one important task is to reconstruct the land mass migrations of the fauna and flora evolving through- out these large-scale geographical alterations. Now Krause et al (5 authors at 4 installations, US IN DE) report the occurrence of a highly specialized and distinctive group of extinct mammals, the Sudamericidae (Gondwanatheria), in the late Cretaceous of Madagascar and India. The authors suggest these new fossil records are the first evidence of gondwanatheres outside South America, and the first indication of cosmopolitanism among late Cretaceous Gondwanan mammals. They also suggest that Antarctica may have served as an important Cretaceous biogeographic link between South America and Indo-Madagascar.

QY: David W. Krause
Nature 4 Dec 97

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