American-European land bridge for dinosaurs and mammals

Prosaurolophus, a duck-billed dinosaur

From the Google cache.

The ‘big’ cache looks like exhausted. However, I still can find some old logs using keywords (not that those keywords are necessarily in the lost and found logs …)

US-European land bridge for dinosaurs and mammals

Date: 12/30/05 at 7:36PM

Mood: Thinking Playing: I’m a little dinosaur, by Jonathan Richman

From the Contra Costa Times (USA):

Fri, Dec. 30, 2005

Marsupial tooth find bolsters land bridge

By Jackie Burrell

MORAGA – The recent discovery of a 66-million-year-old marsupial tooth in the Netherlands provides fresh proof that a land bridge connected the North American and European continents during the age of dinosaurs.

St. Mary’s College dean of science Judd Case and his colleague James Martin say the 2-millimeter fossil, which belongs to a newly discovered, extinct species similar to an opossum, suggests that dinosaurs and small marsupials not only lived in Europe at the same time, but also traveled the same trans-Atlantic migration route from South Dakota to the Netherlands.

“Wow,” said Case. “It changes what we know.”

Taken together with other, recent finds of North American-type duck-bill dinosaurs and certain types of snakes in Northern Europe, it appears that animals used temporary land bridges to travel across the high polar latitudes 10 million years earlier than paleontologists had thought.

The tooth may be tiny, said Case, but it will have a major impact on scientists’ views of Cretaceous climate, geography and life.

Amateur collectors Roland Meuris and Frans Smet were looking for shark tooth fossils in a quarry near Maastricht, Netherlands, in 2002 when they came across an intriguing rock sample from the Cretaceous period.

When Smet spotted what he thought were mammal teeth, he contacted the nearby Natuurhistorisch Museum Maastricht, which specializes in fossils.

His timing was perfect. James Martin was researching marine reptiles in Maastricht when the museum’s fossil experts asked his opinion of the small, odd tooth.

The South Dakota paleontologist had collaborated frequently with Case on dig projects.

The pair made headlines last year with a spectacular Antarctic dinosaur find.

And last January, Case published a paper on a startling new North American find — 75-million-year-old opossum-like marsupial fossils that were 20 million years older than expected.

Martin knew exactly what he was looking at in Maastricht.

“He said, ‘Wow!'” Case remembered.

“He told me where it’s from and when it’s from, and I said, ‘Wow!'”

The Netherlands discovery — dubbed Maastrichtidelphys meurismeti to honor collectors Meuris and Smet — fills an intriguing gap in the fossil record.

Scientists have long known that dinosaurs and small mammals co-existed during the so-called Dinosaur Age, but fossilized mammal skeletons are rare.

Most primitive mammal studies rely on teeth.

Using scanning electron microscopy to examine surface details, scientists can identify species with a single tooth.

In this case, the upper molar belonged to the new marsupial species found in Canada, Montana, Wyoming and South Dakota — and now, the Netherlands.

But how did a mouse-sized creature cross the Atlantic Ocean?

Earth’s geography was very different back then, said Case.

The Atlantic was only half as wide. Sea levels were lower — and significantly lower at two points, around 71 and 67 million years ago.

And continents were connected. Case and Martin believe animals hopped from land mass to land mass above the 70-degree latitude line.

“Eastern Canada was attached to Greenland,” said Case.

“The Faroes were stuck on top of Great Britain and Great Britain was connected to the rest of Europe.

It had been felt that North American dinosaurs had made a one-time only entry into Europe — but no.”

The discovery of a North American marsupial and duck-billed dinosaurs in Maastricht indicates that the polar crossing was no chilly experiment, but a temperate migration path in a world filled with new, flowering plants.

“While the dinosaurs were munching on leaves, these little guys were probably eating insects and these new flowers,” said Case. “It’s co-evolution.”