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SCIENCE & TECHNOLOGY 2: Fossil Record Gaps Filling

This month, scientists in Africa and Asia have discovered ancient fossils that help close some of the gaps in the fossil record, and help explain to us how certain animals evolved and spread around the world.

Last week, a team of researchers in Ethiopia announced they had discovered the fossils of six extinct species of mammals, including ancient relatives of modern elephants and rhinos. Researchers are always happy to find new fossil specimens, but this find was especially exciting because the fossils dated to about 27 million years ago; until this discovery scientists didn't really know what was happening in the evolution of mammals in Africa at that time.

Scientists had seen fossils and relative fossils of these species before, but they had not yet found any that dated to the period between 24-32 million years ago, a period scientists had considered "missing years" in the fossil record. Now they are able to determine which survived the invasion of Eurasian mammals (including ancestors of modern lions, antelopes, and giraffes) that began about 24 million years ago, and which did not. They have also confirmed that the ancestors of elephant originated in Africa and spread around the world.

This week, a group of researchers in China announced that they had discovered the oldest known marsupial fossil, indicating that marsupials (mammals with pouches, like opossums and kangaroos) originated in Eurasia.

The marsupial fossil, about the size of a mouse, was found in a rock formation that dates back about 125 million years. The same area also produced the oldest placental mammal fossils yet found. The date of the marsupial fossil will help scientists figure out the history of mammal evolution.

--Written by Nia Williams

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