A team of geologists and paleontologists has agreed on an issue that you might have not realized was still in question: an asteroid, and the fallout from its impact, killed the dinosaurs. Some dinosaur experts were holding out on blaming the asteroid, saying that dinosaurs were already on their way out. The scientists say they're getting a better understanding of the "tempo" of dinosaur extinction.
Dinosaurs were unlucky. A new study published in the journal Biological Reviews says that if the asteroid had hit the earth a few million years before or after it did…history might have looked a lot different. It all has to do with what the earth looked like over 75 million years ago. Back then, there was a giant sea from the Gulf of Mexico up into Canada that split North America in half. That created a geography that supported a lot of different species that were native to discrete, relatively small locations. Then about 6 to 7 million years before the dinosaurs went extinct, the sea went away and all those little dinosaur communities started coming together. Here’s Dr. Dan Peppe from Baylor University. He’s one of the authors of the new study, which focused on the diversity of dinosaur species at this time.
"And so what we is in the meat-eating dinosaurs, there’s no effect in terms of how many species there are their diversity and that stuff," Peppe said. "But what we do see is the really big herbivores, the classic triceratops, the duckbill dinosaur, those are sort of declining in diversity sort of."
About a 10 percent decline, which doesn’t sound like an incredibly dramatic change, but Peppe says it was enough to make the food chain vulnerable. There’s not a lot of diversity within those huge herbivore species. Then the asteroid comes along, sending ash up into the sky and clouding the atmosphere for years. Plants died, then plant eaters died, then things that ate the plant eaters died. Dr. Peppe says the system was unstable, and the push of the meteor caused the extinction.
"And maybe 5 million years before when the base of that food chain is more diverse, there’s more species on the landscape, you knock out one or two it doesn’t really have a big effect," Peppe said. "But right at this period of time, 66 million years ago, you only have a few species, you knock them out and the whole food web falls apart."
A lot of new data has come onto the dinosaur scene to help the scientists make these conclusions. Part of that data came from technological advances: CT scanning fossils have given scientists new looks at exactly how the internal anatomies of these creatures worked. And we’ve entered a pretty prolific period of dinosaur discoveries. According to an article from 2008, a new dinosaur species is named every week or two.
"Some of places in China and South America, it’s unexplored territory so you’re going out there and you’re finding new dinosaurs and you’re finding new species practically every time where out there," Peppe said.