[meteorite-list] Cold Spelt End Of Dinosaurs

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:08:19 2004
Message-ID: <200209010507.WAA02888_at_zagami.jpl.nasa.gov>

http://news.bbc.co.uk/1/hi/sci/tech/2225779.stm

Cold spelt end of dinosaurs
BBC News
August 31, 2002
           
Dinosaurs could not cope with climate change
Cold was killing dinosaurs long before the asteroid commonly
thought to have been their downfall hit, according to scientists.

That asteroid 65 million years ago in the past Cretaceous period was
probably the "final straw".

But Australian experts say up to half of all dinosaurs were gone by
then, because the climate had got too cold for them to bear.

Fossil evidence from the Drumheller valley in Alberta, Canada,
covering 7m years before the asteroid hit, shows that average
temperatures dropped from 25°C to 15°C.

Many cold-blooded reptiles such as crocodiles, turtles and many
large plant-eating dinosaurs died out as the climate cooled.

Oxygen isotope readings from fossils show the temperatures at
which they formed, so scientists can track the climate change
over time.

They found there was also a decrease in annual rainfall over the
period where species died out.

But, David Eberth of the Royal Tyrell Museum of Palaeontology,
who carried out the research, said it was unclear why dinosaurs were
so dramatically affected.

Body temperature

Dr Angela Milner, associate keeper of palaeontology at the Natural
History Museum, told BBC News Online: "A lot of people have
suggested that climate change is the reason dinosaurs started to
decline.

"But this research, using isotopes records, shows categorically there
was quite a big temperature drop."

Dr Milner said cold-blooded dinosaurs would have been able to bear
a colder climate for a short time because their size would have meant
they could keep their body temperature constant.

But they would have been unable to cope for very long.

Dr Milner added: "In popular perception, dinosaurs died out because
of the asteroid. But the actual evidence from the fossils doesn't
support that in the way some people like to think.

"But that may well have been the final straw that broke the
remaining camels' backs."

The research is featured in Chemistry and Industry.
Received on Sun 01 Sep 2002 01:07:35 AM PDT