Ancient "Chewing" Reptile Linked With Leap in Animal Diversity

National Geographic News
June 7, 2001

Researchers have discovered the first known example of a land-based vertebrate that had the ability to fully chew and digest plants for food. This trait is important because it enables animals to break down and efficiently process many different kinds of vegetation.

The development of a sophisticated chewing ability paved the way to the emergence of a wide variety of plant-eating animals, say the researchers, who reported their findings in the June 7 issue of the journal Nature.

The evidence came from the fossilized skull of what the scientists said was a gangly, big-eyed, large-toothed land-dwelling reptile, called Suminia getmanovi. It lived 260 million years ago—about 50 million years before dinosaurs.

"The real boost in the success of vertebrates on land started with the ability to process plant material efficiently," said Robert Reisz, a professor at the University of Toronto in Mississauga. His collaborator and co-author of the paper in Nature was Natalia Rybczynski, who is now at Duke University.

The research was funded by the National Geographic Society and the Natural Sciences and Engineering Research Council of Canada.

Changing Ecosystem

The advent of chewing as seen in Suminia paved the way to the first great burst of diversity among terrestrial herbivores, according to the researchers. This diversity is mirrored today in the ecosystem of land-based animals that evolved over time.

The modern-day animal kingdom has many herbivores, which serve as food for a much smaller number of carnivores. Plant-eating species such as gazelles and antelope are abundant, for example, while carnivores such as lions and leopards are relatively much more scarce.

"There is a link between the time when land-dwelling herbivores started processing food in the mouth and a great increase in animal diversity," said Reisz. "So you can say that the evolution of the modern terrestrial ecosystem, with lots of herbivores supporting a few top predators, is based on animals efficiently eating the greenery on land."

Before this evolution of diversity, the scientists explained, the ecosystem was very different.

According to Reisz, the first terrestrial herbivore appeared on land about 290 million years ago. But herbivores at that time had a more rudimentary style of eating. They tore the leaves off the plant and swallowed them whole, and the leaves were then processed in the animals' guts.

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