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When John Ruben first laid eyes on a high-quality photo of the so-called
"feathered" dinosaur from China last year, he was stunned. It wasn't the
featherlike structures that riveted his attention--he dismissed them as
collagen fibers --but the theropod dinosaur's innards, which were outlined
in the slab of stone. "My eyes popped out," recalls Ruben, a respiratory
physiology expert at Oregon State University in Corvallis. "I realized that
here was the first evidence in the soft tissue that theropods had the same
kind of compartmentalization of lungs, liver, and intestines that you would
find in a crocodile"--and not in a bird.

To prove that notion, Ruben and his graduate students sectioned crocodiles
and other reptiles and found that their lung structures resembled the images
of several flattened fossil dinosaurs from China. On page 1267, Ruben uses
this lung evidence to argue not only that dinosaurs were incapable of the
high rates of gas exchange needed for warm-bloodedness, but also that their
bellowslike lungs could not have evolved into the high-performance lungs of
modern birds. Thus, he challenges two of the reigning hypotheses concerning
dinosaurs: that they were warm-blooded and that they gave rise to birds.

Coming hot on the heels of another controversial paper that concludes that
digits in bird wings could not have developed from dinosaur forelimbs
(Science, 24 October, p. 666), Ruben's report is part of a "one-two punch to
the dinosaur origins of birds hypothesis," says paleontologist James Farlow
of Indiana University-Purdue University in Fort Wayne. But while many
dinosaur experts say they welcome Ruben's novel approach, few are willing to
embrace his conclusions so far. "This is exactly the kind of research we
need," says Lawrence Witmer, an evolutionary biologist at Ohio University
College of Osteopathic Medicine in Athens. And it's definitely weakening the
case for warm-blooded dinosaurs. But many researchers, including Farlow and
Witmer, think there's persuasive evidence that birds are descendants of
dinosaurs. Says Farlow: "[This] is like a breath of fresh air, but it's
going to ruffle a lot of feathers."

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Lung Fossils Suggest Dinos Breathed in Cold Blood

Science
25-DEC-97
By=20Ann Gibbons=20

When John Ruben first laid eyes on a high-quality photo of the =so-called=20"feathered" dinosaur from China last year, he was stunned. It =wasn't=20the featherlike structures that riveted his attention--he dismissed them =as=20collagen fibers --but the theropod dinosaur's innards, which were =outlined in=20the slab of stone. "My eyes popped out," recalls Ruben, a =respiratory=20physiology expert at Oregon State University in Corvallis. "I =realized that=20here was the first evidence in the soft tissue that theropods had the =same kind=20of compartmentalization of lungs, liver, and intestines that you would =find in a=20crocodile"--and not in a bird.

To prove that notion, Ruben and his graduate students sectioned =crocodiles=20and other reptiles and found that their lung structures resembled the =images of=20several flattened fossil dinosaurs from China. On page 1267, Ruben uses =this=20lung evidence to argue not only that dinosaurs were incapable of the =high rates=20of gas exchange needed for warm-bloodedness, but also that their =bellowslike=20lungs could not have evolved into the high-performance lungs of modern =birds.=20Thus, he challenges two of the reigning hypotheses concerning dinosaurs: =that=20they were warm-blooded and that they gave rise to birds.

Coming hot on the heels of another controversial paper that concludes =that=20digits in bird wings could not have developed from dinosaur forelimbs =(Science,=2024 October, p. 666), Ruben's report is part of a "one-two punch to =the=20dinosaur origins of birds hypothesis," says paleontologist James =Farlow of=20Indiana University-Purdue University in Fort Wayne. But while many =dinosaur=20experts say they welcome Ruben's novel approach, few are willing to =embrace his=20conclusions so far. "This is exactly the kind of research we =need,"=20says Lawrence Witmer, an evolutionary biologist at Ohio University =College of=20Osteopathic Medicine in Athens. And it's definitely weakening the case =for=20warm-blooded dinosaurs. But many researchers, including Farlow and =Witmer, think=20there's persuasive evidence that birds are descendants of dinosaurs. =Says=20Farlow: "[This] is like a breath of fresh air, but it's going to =ruffle a=20lot of feathers."

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