Peter Gronemann [creativecommons license] via Wikimedia CommonsWhen birds breathe, air flows through their lungs in a unidirectional pattern, once thought to be a unique adaptation to meet the high oxygen demands of flight. But when similar unidirectional flow patterns were discovered in the lungs of crocodilians, paleobiologists began to consider that this trait may have developed in an ancestor common to birds and crocodilians and also been present in other archosaurs, including extinct relatives such as pterosaurs and dinosaurs, 250 million years ago. Researchers at University of Utah (Salt Lake City) wondered if the trait might be even older than that. To find out, they examined airflow patterns in the lungs of monitor lizards, whose lineage split away from the archosaurs about 270 million years ago.
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