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Fwd: Low Oxygen Could Have Benefited Dinosaurs

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  • Patrick Neuman
    Repeat post from P&C Nov 7, 2003 fyi ... WASHINGTON (Reuters) - Low oxygen levels could have triggered two giant extinctions hundreds of millions of years ago,
    Message 1 of 1 , Feb 1, 2004
      Repeat post from P&C Nov 7, 2003
      --- In Paleontology_and_Climate@yahoogroups.com, npat1@j... wrote:
      WASHINGTON (Reuters) - Low oxygen levels could have triggered two
      extinctions hundreds of millions of years ago, allowing the dinosaurs
      reign supreme over the ancestors of mammals, U.S. researchers said on

      Dinosaurs first appeared during a long period of low oxygen and
      developed highly efficient breathing mechanisms that allowed them to
      thrive while many other species became extinct.

      The researchers arrived at the theory by tying in what is known about
      physiology of dinosaurs with recent geological evidence suggesting
      from 275 million to 175 million years ago, oxygen levels stayed very
      -- comparable to levels found now at altitudes of 14,000 feet.

      Peter Ward, a University of Washington paleontologist, said he
      low oxygen and hot greenhouse conditions caused by intense volcanic
      activity may have caused widespread extinctions 250 million years
      ago, at
      the boundary between the Permian and Triassic periods, and about 200
      million years ago, at the boundary between the Triassic and Jurassic

      The Permian-Triassic extinction is believed to have eradicated 90
      of all species on Earth, including most protomammals, the immediate
      ancestors of true mammals.

      The Triassic-Jurassic extinction killed more than half the species,
      including many mammals and mammal-like reptiles. But dinosaurs

      Ward said he put together three pieces of the puzzle -- the extremely
      breathing systems of birds, the finding that many dinosaurs had
      physiology, and a report that came out earlier this year showing that
      oxygen levels were low during the two extinctions.

      "Someone told me they had heard of or seen geese flying above (Mount)
      Everest -- at 31,000 feet," said Ward, who presents his findings next
      week to a meeting of the Geological Society of America.

      The air is thin up there. "If you put a human at 30,000 feet they'd
      very, very, quite dead. And the birds are not only up there, they are
      doing major heavy exercise," Ward said

      Birds and dinosaurs both have holes in their bones. And many of the
      largest dinosaurs, such as brontosaurus or apatosaurus, seem to have
      lungs attached to a series of thin-walled air sacs that may have acted
      something like bellows to move air through the body.

      "The reason the birds developed these systems is that they arose from
      halfway through the Jurassic Period. They are how the dinosaurs
      survived," Ward

      "The literature always said that the reason birds had sacs was so they
      could breathe when they fly. But I don't know of any brontosaurus that
      could fly," he added.

      "However, when we considered that birds fly at altitudes where oxygen
      significantly lower, we finally put it all together with the fact that
      the oxygen level at the surface was only 10 percent to 11 percent at
      time the dinosaurs evolved."

      Currently at sea level, atmospheric oxygen levels are 21 percent. If
      giant dinosaurs had to breathe in a low-atmosphere environment, then
      an efficient breathing system would have given them a survival

      "You'd be really favored for survival in very bad, nasty, low-oxygen
      world," Ward said.
      Dinosaurs dominated the world for hundreds of millions of years,
      perishing only
      65 million years ago. Most scientists agree the impact of an asteroid
      meteor was the catalyst.

      Low Oxygen Could Have Benefited Dinosaurs
      By Maggie Fox, Health and Science Correspondent

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      --- End forwarded message ---
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