Some 40 million years before rock singer Jim Morrison's lyrics¹ earned him the moniker（绰号，名字） "the Lizard² King," an actual king lizard roamed the hot tropical forests of Southeast Asia, competing with mammals for food and other resources. A team of U.S. paleontologists, led by Jason Head of the University of Nebraska-Lincoln, describes fossils of the giant lizard from Myanmar this week in the scientific journal Proceedings³ of the Royal Society B. Their analysis shows that it is one of the biggest known lizards⁴ ever to have lived on land.

 

The creature's scientific name is Barbaturex morrisoni -- which means "Lizard King," in honor of the aforementioned（上述的） Doors singer.

 

At almost six feet long and weighing upwards⁵ of 60 pounds, the lizard provides new and important clues on the evolution of plant-eating reptiles⁶ and their relationship to global climate and competition with mammals.

 

In today's world, plant-eating lizards like iguanas⁷（鬃蜥） and agamids are much smaller than large mammal herbivores（食草动物）. The largest lizards, like the giant, carnivorous Komodo dragon, are limited to islands that are light on mammal predators⁸. It is not known, however, if lizards are limited in size by competition with mammals, or by temperatures of modern climates, Head said.

 

But B. morrisoni lived in an ecosystem⁹ with a diversity of both herbivorous and carnivorous mammals during a warm age in Earth's history -- 36 to 40 million years ago -- when there was no ice at the poles and atmospheric¹⁰ carbon dioxide levels were very high. The creature was larger than most of the mammals with which it lived, suggesting that competition or predation by mammals did not restrict its evolution into a giant.

 

"We think the warm climate during that period of time allowed the evolution of a large body size and the ability of plant-eating lizards to successfully compete in mammal faunas," Head said.

 

"You can't fully¹¹ understand the evolution of ecosystems¹² in the modern world without looking at the ones that preceded them. We would've never known this by looking at lizards today. By going back in time using the fossil record, we can find unique information on the origin of modern ecosystems."

 

Head worked with Patricia Holroyd of University of California, Berkeley, Gregg Gunnell of Duke University, and Russell Ciochon of the University of Iowa on identifying and analyzing¹³ B. morrisoni.

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