The advent of chewing by a group of herbivores 260 million years ago may have signaled one of the first great bursts of vertebrate life on land, say paleontologists from the University of Toronto and Duke University.

"The real boost in the success of vertebrates on land started with the ability to process plant material efficiently," says University of Toronto at Mississauga paleontology professor Robert Reisz in the June 7 issue of Nature, who co-authored the paper with graduate student Natalia Rybczynski, who later moved on to Duke University.

According to Reisz, the first terrestrial herbivore appeared on land about 290 million years ago. But herbivores then had a fairly rudimentary form of eating - they simply tore the leaves off the plant and swallowed them whole, leaving most of the processing to take place in the guts.

Suminia getmanovi, however, evolved a far more innovative and efficient way of eating by first chewing and shredding the leaves into small bits before swallowing, thereby allowing maximum absorption of the plant's energy and nutrients. The advent of chewing in this species of terrestrial herbivore is also associated with the Earth's first great burst in the diversity and number of terrestrial herbivorous vertebrates, says Reisz.

"There is a link between the time when land-dwelling herbivores started processing food in the mouth and a great increase in animal diversity," he notes. "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."

This type of terrestrial ecosystem is mirrored in modern-day animals. Today we see an abundance of plant-eating herbivores like gazelles and antelope with relatively few carnivores, such as lions and leopards.

Discovered in 1990, the skull of Suminia looks something like that of a little monkey or a rodent, with hug
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Contact: Janet Wong
jf.wong@utoronto.ca
416-978-6974
University of Toronto
6-Jun-2001