Dinosaurs were in their prime when meteorite impact wiped them out

The common perception that dinosaurs were edging towards extinction when a huge meteorite wiped them out 65 million years ago is false, says a new study that claims the animals were in their prime when disaster struck.

The common perception that dinosaurs were edging towards extinction when a huge meteorite wiped them out 65 million years ago is false, says a new study that claims the animals were in their prime when disaster struck.

The variety of species existing around the end of the Cretaceous period suggests that they were diversifying at a remarkable rate, with an explosion of genetic diversity that was reflected in their success dominating the planet.

Scientists from the University of Rhode Island at Kingston, in the United States, established that at least 245 dinosaur genera - the "families" from which species emerge - lived during the late Cretaceous era, from 99 million to 65 million years ago.

They included some of the best known dinosaurs, such as tyrannosaurus rex and the three-horned triceratops.

Peter Sheehan, from the Milwaukee Public Museum, who took part in the research, told New Scientist magazine: "The lifestyles of dinosaurs became much more diverse. By the late Cretaceous, we have much more specialised animals."

The first dinosaurs evolved about 230 million years ago and were all much the same.

By the late Jurassic period, which began about 160 million years ago, they had produced about 40 different genera, or species families.

Then in the Cretaceous era which followed there was an explosion of dinosaur diversity, according to a new analysis of fossils from around the world.

Dr Sheehan said the diversity of plant-eating dinosaurs of the period was "absolutely breathtaking". For example, hadrosaurs evolved a duck-billed jaw filled with teeth for chewing vegetation, while the rhinoceros-like ceratopsians grew elaborate horns.

But the controversy over the dinosaurs' evolutionary path looks likely to continue: on Tuesday a paper published in the scientific journal Trends in Ecology and Evolution by Professor David Penny of Massey University in New Zealand and Dr Matt Phillips of Oxford University claimed the precise opposite - that birds and mammals began to "out-compete" dinosaurs about 80 to 90 million years ago, well before the end of the Cretaceous era.

"The combined evidence from fossils and molecules appears to support an expansion of birds and mammals, and a decline of pterosaurs and dinosaurs, starting many millions of years before the end of the Cretaceous," the scientists wrote.

What is not in doubt however is that there was a serious meteor strike on the Earth roughly 65 million years ago, in the Bay of Mexico. That is reckoned to have thrown up so much dust into the atmosphere that it cooled the planet abruptly, making it much harder for the cold-blooded dinosaurs to survive, and giving warm-blooded animals including mammals the evolutionary edge.