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Dinosaurs Breathed Like Birds



http://www.nature.com/news/2005/050711/full/050711-8.html

Dinosaurs' hollow bones may have given them the puff to lead active
lifestyles. A fossil find shows that the group of dinosaurs that included
Velociraptor and Tyrannosaurus rex probably used the same super-efficient
respiratory system that birds have today.

The fossil, which is of a carnivorous dinosaur called Majungatholus
atopus, shows that its bones included spaces for storing air. This would
have allowed the species to have the quick metabolism necessary for an
active predatory lifestyle.

Birds have fast metabolic rates thanks to their efficient way of
extracting oxygen from the air. They have two lungs, as mammals do, but
the airflow through them is controlled by a complex system of air sacs
throughout the body. Most birds have nine such sacs, which also extend
through their hollow bones.

Patrick O'Connor, of Ohio University in Athens, and Leon Claessens, of
Harvard University in Cambridge, Massachusetts, compared the structure of
air sacs in M. atopus's vertebrae to those in more than 200 living birds.
The structures were very similar, they report in this week's Nature.
...