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Prehistoric lizard-like creature called a treetop trailblazer

September 06, 2009|William Mullen

CHICAGO — About 260 million years ago, a scared and hungry animal, out-competed for food by larger beasts and chased by nasty predators, left the ground and climbed a tree.

The creature was a slender, leaf-eating, lizard-like cousin of animals that would evolve into the first mammals 50 million years later -- setting the stage for all manner of modern creatures who take to the treetops, including primates who left the trees but now return to pick apples, recover cats and build treehouses.

But until Suminia getmanovi first learned to climb, the only animals living above ground level in the trees were insects. With the first birds not appearing for another 110 million years, Suminia had the treetops to itself for 10 million years.

It was the first animal with a spine to take up high-rise, treetop living, according to the research of a Field Museum scientist and a colleague reported in the British online journal Proceedings of the Royal Society.

Jorg Frobisch, a Field Museum post-doctoral paleontologist, and Robert Reisz, from the University of Toronto, figured out Suminia was an early tree-dweller by paying attention to its unusual physical attributes, in this case in its fossil bones.

"It is a relatively small animal, 20 inches from tip of snout to tip of tail," Frobisch said. "But it has very elongated fingers like we see in a modern-day climbing animal like primates and chameleons, and they have curved claws showing they could hang on to branches.

"Most importantly, they had opposable, thumb-like digits for grasping, and it also had a prehensile tail to hang on to branches. Without a doubt, it was an arboreal, climbing animal."

Suminia went extinct about 250 million years ago, and it took 100 million more years before any other vertebrate animal would learn to climb trees. But eventually trees became the preferred dwelling place for a veritable menagerie of critters, including squirrels, monkeys, snakes and lizards.

All of them live in trees for the same reasons Suminia did, to escape from predators or to find food, or both.

"Suminia is a trailblazer, the first vertebrate to get into the arboreal niche," said Zhe-Xi Luo, curator of vertebrate paleontology at Pittsburgh's Carnegie Museum of Natural History.

The Suminia fossils Frobisch and Reisz studied lived at a time and place where larger and stronger kinds of plant-eaters easily muscled Suminia out of the way for the best feeding places.

At the same time, Suminia was a prime prey animal for meat-eating gorgonopsians.

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wmullen@tribune.com

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