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BEIJING, Feb. 25 -- Scientists have
discovered fossils of a swimming, fish-eating mammal that lived 164
million years ago, showing that mammals diversified much earlier than thought,
even in an age dominated by dinosaurs.
This beaver-like mammal,
Castorocauda lutrasimilis, would have taken a dip about 164 million years
ago (Image: Mark A
Klinger/CMNH) | In the
conventional view, the earliest mammals were small, primitive shrewlike
creatures that did not begin to explore the world's varied environments until
the dinosaurs died out 65 million years ago.
The discovery says that the extinct species was
a furry, fish-eating swimmer and burrower a bit bigger than a tree squirrel,
with an otter-like body, teeth like a seal, webbed hind feet and a flat tail
like a beaver. It reminds scientists of the modern platypus.
The animal is the earliest swimming mammal to have been
found and was the most primitive mammal to be preserved with fur, which is
important to helping keep a constant body temperature, according to the
scientists.
The surprising discovery, made in 2004 in the abundant
fossil beds of Liaoning province, China, is being reported in the journal
Science by an international team led by Qiang Ji of Nanjing University.
In the article, Ji and other researchers from the Chinese
Academy of Geological Sciences in Beijing and the Carnegie Museum of Natural
History in Pittsburgh said the fossil skeleton showed that some mammals occupied
more diverse ecological niches than had been suspected.
Thomas Martin of the Senckenberg Research Institute in
Frankfurt, Germany, said the discovery pushed back the mammal conquest of the
waters by about 100 million years.
It's the first evidence that some ancient mammals were
semiaquatic, indicating a greater diversification than previously thought, the
researchers said.
The new animal has been given the name Castorocauda
lutrasimilis: castoro from the Latin for beaver, cauda for tail, lutra for river
otter and similis meaning similar. Enditem
(Agencies) | 
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