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The Lizard King rises

The bearded dragon, a modern relative of the Lizard King, grows to less than half a meter in length and lives in Australia.

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Copyright Shutterstock.com/Darren Green

The trouble with being a lizard is that your mammal neighbors are always trying to eat your dinner, or make you into their dinner, wielding a competitive advantage scientists have long attributed to their warm-blooded metabolism. For this reason, large lizards like the Komodo dragon are extremely rare, and only occur in isolated island environments that lack other predators. Now, a giant fossil species of herbivorous lizard that appears to have happily coexisted with various large mammal species has been identified in Eocene-aged rocks from Myanmar. Scientists christened it Barbaturex morrisoni (which translates to “bearded king Morrison”) in honor of the other Lizard King, singer Jim Morrison of The Doors.

In the study, led by Jason Head at the University of Nebraska at Lincoln and published in the Proceedings of the Royal Society B, the researchers estimate the size and habits of B. morrisoni by extrapolating known relationships between tooth characteristics and body size in modern lizards. The Lizard King likely approached 2 meters in length and weighed about 30 kilograms. They determined its vegetarian diet from the lack of carnivorous jaw traits.

The scientists also reconstructed the Eocene climate from the fossil. The body mass of cold-blooded lizards scales with ambient temperature, meaning B. morrisoni’s environment was probably at least 6 degrees Celsius warmer than today, consistent with other paleoclimate reconstructions. B. morrisoni’s ability to coexist with large mammals suggests that climate may play a more important role than previously recognized in determining the maximum attainable size of modern lizards, and that mammals’ warm-blooded metabolism may not confer such a competitive advantage after all.

Julia Rosen
Monday, November 11, 2013