Monitor Lizards Can Breathe Unidirectionally Just Like Birds

Monitor lizards capture oxygen from air both when inhaling and exhaling, a feat normally associated with birds. Many scientists believe birds developed the adaptation to cope with the enormous requirements of energy needed to take flight, and the discovery of “unidirectional breathing” in the savannah monitor lizard raises questions about when and why the trait first evolved.

Monitor lizards extract oxygen both when they inhale and exhale, perhaps explaining why they are so successful as a species

“To go and find a similar air-flow pattern in animals as distantly related [to birds] as monitor lizards is mind blowing,” says Mathew Wedel, an evolutionary biologist at Western University of Health Sciences in Pomona, California, who was not involved in the discovery.

“When you pull the lungs out it just looks like a bag with chambers. It doesn’t look anything like the bird lung.” But computed tomography (CT) scans revealed a large chamber, with a series of up to 11 brachial tubes branching off in parallel and linked to one another via perforations—a set-up that could enable one-way flow. – Colleen Farmer at the University of Utah in Salt Lake City