The dinosaurs that held dominion over the Earth in the Jurassic Period didn't rule the lands because they out-competed every rival, a new study says. Researchers studied fossil evidence from an earlier epoch, the Triassic Period, and say that dinosaurs showed no evidence of being better adapted to their environment than their challengers.
"For a long time it was thought that there was something special about the dinosaurs that helped them become more successful during the Triassic, the first 30 million years of their history, but this isn't true," said lead author of the study, Steve Brusatte [LiveScience].
Instead they may have just been lucky enough to survive a drastic climate shift when their rivals didn't. Researchers compared fossils from the 30 million years in the Triassic when dinosaurs coexisted with crurotarsan archosaurs, a group whose only living relative is crocodiles. They found that not only did the groups evolve at the same rate, but the crurotarsans even developed a wider range of body types than dinosaurs, suggesting that
the group as a whole was more successful at developing to live in different habitats and ecosystems [Telegraph].
An observer comparing the two groups in the late Triassic would have expected the crurotarsans to eventually dominate, says Brusatte.... Yet all the crurotarsans bar the crocodiles were wiped out 200 million years ago, when rapid climate change caused a mass extinction. Dinosaurs "pretty much got lucky" and sailed through to dominate ecosystems for another 135 million years, he says [New Scientist].
The study, which will be published tomorrow in Science [subscription required], doesn't suggest any reason why the dinosaurs made it through the extinction event. Some experts say that attributing their success to luck is an unsatisfying explanation, and say that the dinosaurs may have had an edge that
proved crucial only at the end of the Triassic, when life on Earth was threatened on a mass scale.... [But] Brusatte, the study co-author, said that even if the dinosaurs were competing with the crurotarsans, it wasn't competition in the classical sense, and it was much briefer than previously thought.... "Call it competition if you will, but it's a whole different horse. What we're essentially saying is that without the extinction [event], dinosaurs would have never made it" [National Geographic News].
Catch a glimpse of one of the earliest dinosaurs that tromped through the Triassic in the DISCOVER article, "Brazil's New Dinosaur." Image: Stephen Brusatte, Columbia University