A woman inspects the head of a Tyrannosaurus Rex dinosaur sculpture in Stuttgart, 2007. The age of dinosaurs lasted more than 160 million years, but new research out Thursday suggests their dominance had less to do with their supposed physiological superiority and more to do with blind luck. [File Photo: AFP/DDP]

The age of dinosaurs lasted more than 160 million years, but new research out Thursday suggests their dominance had less to do with their supposed physiological superiority and more to do with blind luck.

"For a long time it was thought there was something special about dinosaurs that helped them become more successful during the first 30 million years of their history, but this isn't true," said Steve Brusatte, a researcher at Columbia University in New York and co-author of the study.

"If any of us were there during the Triassic and asked which group would rule the world for the next 130 million years, we would have identified the crurotarsans, their competitors, whose descendants are crocodiles," he added.

At the end of the Triassic, around 200 million years ago, crurotarsans and dinosaurs were probably in competition for the same resources. Because dinosaurs survived such a long time they have were thought to have evolved faster and adapted better than their competitors.

But the new research, published in the journal Science on September 12, suggests it was the crurotarsans who had the upper hand.

After studying nearly 500 skeletal characteristics from 64 species, researchers say that in terms of diversity of size, body types, diet, and lifestyle, crurotarsans had the evolutionary edge.

Compared with modern day crocodiles, Triassic-era crurotarsans were surprisingly diverse. There were huge biped predators, and quadrupeds such as the Deinosuchus (meaning 'Terrible Crocodile') that ate herbivorous dinosaurs.

An extreme spike in global warming around 200 million years ago, probably due to a meteor impact, led to the sudden extinction of crurotarsans but somehow spared the dinosaurs.

With their competitors suddenly gone, dinosaurs became the dominant species on Earth for the next 135 million years, when another catastrophic meteor impact ended their reign.

"The analysis of our data makes it difficult to say that dinosaurs were superior," said Brusatte.

"They just lucked out when the crurotarsans were hit hard," he added.

There is no scientific answer to why crurotarsans disappeared and the dinosaurs survived in the fallout from the meteor impact 200 million years ago, said co-author Michael Benton, a paleontologist at the University of Bristol in the United Kingdom.

"Many people like to think that evolution is progressive: mammals are better than dinosaurs because they came later. This is like progressive improvements in car technology: a Ford Taurus is demonstrably better than a Model T," he said.

The ideas of progressive "improvement" in evolution, and humankind's place in the world, are so pervasive that Benton admits "it may be hard" for the study's findings to be accepted.

But, he said, just as dinosaurs reigned over the earth "largely by chance," mammals achieved their dominant position in much the same way, after the dinosaurs became extinct.