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mice first mammal to migrate from North America to Europe
Species of rodents crossed Thulean Land Bridge 50 million years
Fossilized teeth found within the Arctic Circle of now extinct
rodents have provided the first documented occurrence of mammals having
a North American origin and then migrating to Western Europe across
a North Atlantic landmass.
In an article published in a recent issue of Canadian Journal of
Earth Sciences, Carnegie Museum of Natural History paleontologist
Mary Dawson describes the first documented eastward migration of North
American mammals into Western Europe. Plate tectonics theory proposes
that this area was once a land connection between North America and
Western Europe called the Thulean Land Bridge.
"We knew there was connection through plate tectonics evidence
and because there existed many closely related animals in North America
and Western Europe in the Early Eocene (approximately 50 million years
ago when the age of mammals was just beginning)," said Dr. Dawson.
Until now, scientists were unsure how these relationships existed. During
the Early Eocene there was a large, north-south body of water called
the Turgai Strait separating Asia from western Europe. This natural
barrier prevented migration of animals between today's Europe and Asia
until it dried up about 45 million years ago.
"The fossil record from the Arctic tells us the route these animals
took," Dr. Dawson said. "We now can trace one group from an
origin in North America to Western Europe over the North Atlantic land
bridge, which was very similar to the better-known Bering Strait land
bridge between Asia and North America."
The fossils found are small rodents called microparamyines. These animals
originated in North America, moved into Western Europe, and much later
evolved into the dormice of today.
They were unearthed from Canada's high Arctic Ellesmere Island, situated
at about 78 degrees north latitude, an area covered today with tundra
and ice and the current home to polar bears, walruses, seals, musk oxen,
foxes, Arctic wolves, lemmings, and hares, as well as a rich diversity
of bird life.
The Arctic islands of 50 million years ago were far different from the
cold, treeless tundra of today. Fossil remains of crocodiles, turtles,
lizards, monkey-like animals, large Metasequoia trees, lotuses and other
plants describe a climate that was a frost-free, having a warm temperate
climate similar to present day South Carolina.
Dr. Dawson is an expert of fossil mammals, concentrating on early Tertiary
faunas and the evolution of rodents and rabbits. In 1981, she received
the prestigious Arnold Guyot Prize, awarded by the National Geographic
Society in recognition of her research in the Arctic, which produced
fossil evidence that North America and Europe were linked and shared
the same animal types 45 - 50 million years ago.
A native of Michigan, Dr. Dawson received her BS from Michigan State
University and her Ph.D. from the University of Kansas. She came to
Carnegie Museum of Natural History as a research associate in the section
of Vertebrate Paleontology in 1962 and was appointed curator in 1970.
She has also served as acting director of Carnegie Museum of Natural
History and is an adjunct professor, Department of Geology and Planetary
Sciences at the University of Pittsburgh. In 1999, she was named Honorary
Member of the Society of Vertebrate Paleontology.
The National Geographic Society, Polar Continental Shelf Project and
the Canadian Department of Energy, Mines and resources provided funding
for this research.
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information for authors
Section of Vertebrate Paleontology
Carnegie Museum of Natural History
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