University of Chicago paleontologist David Jablonski said he found the aftermath of extinction was even messier than had been believed. Even in a worldwide event -- such as the mass extinction that followed what scientists now think was an asteroid hitting Mexico -- extinction patterns varied from region to region, Jablonski found.
"These are completely unexpected results," Jablonski, who reported his findings in the journal Science, said in a statement. "Maybe not all extinctions are created equal -- it's not only how much you lose, but who." Jablonski was studying what species survived after the mass extinction that killed the dinosaurs 65 million years ago. He found recovery rates in what are now North America and Europe were very different even though they are at roughly the same latitude.
"I was astounded when I found startling differences between Europe and North America," Jablonski said. "In North America, there was a large pulse of 'bloom' taxa (species), a great diversification of a few groups. It was like when weeds move in when a forest is mowed down. But this did not happen across the Atlantic.
Jablonski looked further and found many other differences, not only in what species moved in from other regions, but in which new species evolved and which ones survived the extinction. Previous studies have found that the numbers of invaders coming in after an extinction correlates to how many original species died out, but Jablonski did not find this. Jablonski said further research could shed light on just what does happen after extinctions. Such work could be important now, as human activities cause species to go extinct around the world, he said. "If it really is important not how many species you lose, but which ones, then that can help us understand different responses and even help ameliorate invasion intensities in different regions," Jablonski said.
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11/18/98
LONDON, - Scientists are more certain than ever that a huge asteroid collided with the Earth 65 million years ago and led to the demise of the dinosaurs.
They knew that something big smashed into the planet, probably at the site of the Chicxulub crater on Mexico's Yucatan peninsula, but despite decades of research they are still not sure what it was. But Frank Kyte, a geologist at the University of California at Los Angeles, thinks he has found a fossil meteorite that is a tiny bit of an asteroid that smashed into the Earth all those years ago.
"From what we know of asteroids and what we know of comets I'd say this is much more likely to have come from an asteroid," he said in a telephone interview. The 12.5 mm (0.5 inch) fossil was retrieved from the K/T boundary, the geologic layer of the Earth when the Cretaceous period ended and the Tertiary started, about the same time the dinosaurs began to disappear.
"We really don't understand a lot about what happened to the physical environment at that time. It's only through learning from little bits of data that we'll be able to shed more light on this," said Kyte. He believes the fossil meteorite is another piece of the puzzle that could help to explain what happened to the Earth and the dinosaurs.
In a letter to the science journal Nature published on Wednesday, he said the meteorite is the first K/T boundary sample with sufficient information from textural and chemical data to make inferences about its orgin. "Here we have a meteorite and we can rather defintively say what type of object it came from. It seems to provide reasonably good evidence that this was an asteroidal object as opposed to a cometary object." Kyte's findings support an earlier study by Alexander Shukolyukov, of the Scripps Institution of Oceanography at the University of California, which found extraterrestrial chromium in rocks from the K/T boundary, which also backs up the asteroid theory.
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SAO PAULO (Reuters) - Paleontologists in southern Brazil said Wednesday they had discovered three bones from one of the world's oldest dinosaurs dating back some 200 million years. "The bones belong to a dinosaur in the prosauropod suborder which lived in the Triassic age, making it one of the oldest existing specimens registered in the world," said Max Langer, a paleontologist at the Catholic University in Rio Grande do Sul state.
The dinosaur was a plant-eating, lizard-like animal about the size of a large dog, he said. Researchers working in Santa Maria, 833 miles south of Sao Paulo, found the three bones during a dig that began at the end of January, Langer said. It was the second discovery in southern Brazil of dinosaur bones from the Triassic age. The first specimens were unearthed in Santa Maria in 1936, Langer said.
The original specimens and three others from the same age unearthed in neighboring Argentina belonged to the theropods suborder, which were meat-eating cousins of the prosauropods, he said.
Brazilian paleontologists have discovered dinosaur bones, mostly dating back to the Cretaceous ages, some 100 million years ago, in the west of Sao Paulo and in the country's northeastern coasts.
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