Re: Cretaceous marsupial from Netherlands

[Phil Bigelow <bigelowp@juno.com>]

Is it even possible to conclusively distinguish a "true" marsupial from a
closely related non-marsupial metatherian based on one tooth?  Which
marsupial molar synapomorphies are the key?

<pb>
--

On Fri, 30 Dec 2005 12:39:01 -0500 "bh480@scn.org" <bh480@scn.org>
writes:
> From: Ben Creisler bh480@scn.org
> 
> In case this news item has not been mentioned yet:
> 
> http://www.contracostatimes.com/mld/cctimes/living/science/13514926.htm
> 
> Marsupial tooth find bolsters land bridge
> By Jackie Burrell CONTRA COSTA TIMES
> 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."
> 
> 
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--
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mind?!" - Kramer