Early Beaver-Like Mammal Swam With Dinosaurs
Reuters
WASHINGTON (Feb. 24) - A creature that looked like a beaver, right down to its
flat paddle-like tail and webbed feet, lived 164 million years ago alongside dinosaurs,
U.S. and Chinese researchers reported on Thursday.
It might not have gnawed trees as modern beavers do -- its teeth suggest it ate
fish -- but the little animal had fur and even the inner ear structure of a mammal,
they report in Friday's issue of the journal Science.
Thomas Martin of the Forschungsinstitut Senckenberg in Frankfurt, Germany, said
the finding showed mammals had conquered the water 100 million years earlier than
anyone thought.
"This exciting fossil is a further jigsaw-puzzle piece in a series of recent
discoveries, demonstrating that the diversity and early evolutionary history of
mammals were much more complex than perceived less than a decade ago," Martin
wrote in a commentary.
The fossil was found in the Middle Jurassic Jiulongshan Formation in China, a
deposit rich in the fossils of dinosaurs, early insects and other creatures. It
dates to 164 million years ago.
Qiang Ji and colleagues at Nanjing University in China and the Carnegie Museum
of Natural History in Pittsburgh said the animal, which they named Castorocauda
lutrasimilis, would have weighed just 500 grams (18 ounces).
"It is the most primitive taxon in the mammalian lineage known to have fur
and has a broad, flattened, partly scaly tail analogous to that of modern beavers,"
they wrote.
They found remnants of fur, scales on the tail and, in between the back toes,
webbing.
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without the prior written consent of Reuters. Reuters shall not be liable for
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02/23/06 17:00 ET
Updated: 04:50 PM EST
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Fossil Overturns Ideas of Jurassic Mammals
By RANDOLPH E. SCHMID, AP
APAn artistic reconstruction of the Castorcauda lustrasimilis is shown. The fossil's
discovery is the first evidence that some ancient mammals were semi-aquatic.
Talk About It: Post Thoughts
WASHINGTON (Feb. 23) - The discovery of a furry, beaver-like animal that lived
at the time of dinosaurs has overturned more than a century of scientific thinking
about Jurassic mammals.
The find shows that the ecological role of mammals in the time of dinosaurs was
far greater than previously thought, said Zhe-Xi Luo, curator of vertebrate paleontology
at Carnegie Museum of Natural History in Pittsburgh.
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, Luo said in a telephone interview.
For over a century, the stereotype of mammals living in that era has been of tiny,
shrew-like creatures scurrying about in the underbrush trying to avoid the giant
creatures that dominated the planet, Luo commented.
Now, a research team that included Luo has found that 164 million years ago, the
newly discovered mammal with a flat, scaly tail like a beaver, vertebra like an
otter and teeth like a seal was swimming in lakes and eating fish.
The team, led by Qiang Ji of the Chinese Academy of Geological Sciences in Beijing,
discovered the remains in the Inner Mongolia region of China. They report their
findings in Friday's issue of the journal Science.
Matthew Carrano, curator of dinosaurs at the Smithsonian's National Museum of
Natural History, called the find "a big deal."
An important factor is how specialized the creature was, said Carrano, who was
not part of the research group.
"It gives a hint that early mammals were not just these shadowy creatures
at the time of dinosaurs" but were having their own evolution. There have
been hints of such animals in the past but nothing equal to the remains found
by Luo and colleagues, he said.
Thomas Martin of the Research Institute Senckenberg in Frankfurt, Germany, said
the discovery pushes back the mammal conquest of the waters by more than 100 million
years.
"This exciting fossil is a further jigsaw puzzle piece in a series of recent
discoveries," commented Martin, who was not part of Luo's team.
It's the first evidence that some ancient mammals were semi-aquatic, indicating
a greater diversification than previously thought, the researchers said.
Modern semi-aquatic mammals such as beavers and otters and aquatic mammals like
whales did not appear until between 55 million years ago and 25 million years
ago, according to the researchers.
The new animal is not related to modern beavers or otters but has features similar
to them. Thus the researchers named it Castorocauda lutrasimilis. Castoro from
the Latin for beaver, cauda for tail, lutra for river otter and similis meaning
similar.
The researchers found imprints of the fur, both guard hairs and short, dense under
fur that would have kept water from the skin.
Weighing in at between 1.1 and 1.7 pounds, about the size of a small female platypus,
Castorocauda is also the largest known Jurassic early mammal.
The research was funded by the U.S. National Science Foundation, National Natural
Science Foundation of China, Ministry of Science and Technology of China, Chinese
Ministry of Land Resources, National Geographic Society and Carnegie Museum.
Early Beaver-Like Mammal Swam With Dinosaurs
Reuters
WASHINGTON (Feb. 24) - A creature that looked like a beaver, right down to its
flat paddle-like tail and webbed feet, lived 164 million years ago alongside dinosaurs,
U.S. and Chinese researchers reported on Thursday.
It might not have gnawed trees as modern beavers do -- its teeth suggest it ate
fish -- but the little animal had fur and even the inner ear structure of a mammal,
they report in Friday's issue of the journal Science.
Thomas Martin of the Forschungsinstitut Senckenberg in Frankfurt, Germany, said
the finding showed mammals had conquered the water 100 million years earlier than
anyone thought.
"This exciting fossil is a further jigsaw-puzzle piece in a series of recent
discoveries, demonstrating that the diversity and early evolutionary history of
mammals were much more complex than perceived less than a decade ago," Martin
wrote in a commentary.
The fossil was found in the Middle Jurassic Jiulongshan Formation in China, a
deposit rich in the fossils of dinosaurs, early insects and other creatures. It
dates to 164 million years ago.
Qiang Ji and colleagues at Nanjing University in China and the Carnegie Museum
of Natural History in Pittsburgh said the animal, which they named Castorocauda
lutrasimilis, would have weighed just 500 grams (18 ounces).
"It is the most primitive taxon in the mammalian lineage known to have fur
and has a broad, flattened, partly scaly tail analogous to that of modern beavers,"
they wrote.
They found remnants of fur, scales on the tail and, in between the back toes,
webbing.
Copyright 2006 Reuters Limited. All rights reserved. Republication or redistribution
of Reuters content, including by framing or similar means, is expressly prohibited
without the prior written consent of Reuters. Reuters shall not be liable for
any errors or delays in the content, or for any actions taken in reliance thereon.
All active hyperlinks have been inserted by AOL.
02/23/06 17:00 ET
Updated: 04:50 PM EST
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