Dinos were not superior, just plain lucky to survive mass extinctions

September 12th, 2008 - 12:34 pm ICT by ANI  

Washington, September 12 (ANI): A new study has rebuffed the theory that dinosaurs were superior, stating that comparison to competitors shows that early dinos survived 2 mass extinctions because they were plain lucky.

The study, carried out by Steve Brusatte, a doctoral student at Columbia University who is an affiliate of the American Museum of Natural History, and colleagues, have challenged the dino superiority theory, with the help of new fossil data and math.

By comparing early dinosaurs to their competitors, the crurotarsan ancestors to crocodiles, they have found that dinosaurs were not superior, as has long been thought.

Rather, crurotarsans were the more successful group during the 30 million years they overlapped until the devastating mass extinction 200 million years ago, an event that dinosaurs weathered successfully.

Both dinosaurs and crurotarsans evolved and filled some of the same niches after a massive extinction event that occurred at the end of the Permian (250 million years ago).

For a long time, it was thought that there was something special about dinosaurs that helped them become more successful during the Triassic, the first 30 million years of their history, but this isnt true, said Brusatte.

If any of us were standing by during the Triassic and asked which group would rule the world for the next 130 million years, we would have identified the crurotarsans, not dinosaurs, he added.

Of the crurotarsan group, crocodilians are the only living members.

But, in the Triassic, crurotarsans were amazingly diversefrom giant carnivorous rauisuchians to longsnouted, flesh eating phytosaurs to herbivorous armored aetosaursand they have often been mistaken for dinosaurs in the fossil record, the animals that they probably competed with for the same resources.

Both groups survived an extinction event 228 million years ago, but only a few crurotarsansthe crocodilessqueaked through a period of rapid global warming at the end of the Triassic 200 million years ago.

Dinosaurs faired better during the latter extinction: most types of dinosaurs survived until an asteroid ended their dominance 65 million years ago.

It is because of this stroke of luck that dinosaurs were assumed to be the better competitors.

Brusatte and colleagues tested this assumption by measuring the evolution in both competing groups.

Based on a database of 437 features of the skeletons of 64 species of dinosaurs and crurotarsans, as well as a new phylogenetic tree of these groups, they performed some calculations to look at the evolutionary pattern.

With this information, its difficult to argue that dinosaurs were superior during the Triassic. They just lucked out when the crurotarsans were hit hard at the end Triassic extinction, said Brusatte. (ANI)

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