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The enduringly popular theory that the Chicxulub crater holds the clue to the demise of the dinosaurs, along with some 65 percent of all species 65 million years ago, is challenged in a paper to be published in the Journal of the Geological Society on April 27, 2009.
The crater, discovered in 1978 in northern Yucutan and measuring about 180 kilometres in diameter, records a massive extra-terrestrial impact.
When spherules from the impact were found just below the Cretaceous-Tertiary (K-T) boundary, it was quickly identified as the "smoking gun" responsible for the mass extinction event that took place 65 million years ago.
It was this event which saw the demise of dinosaurs, along with countless other plant and animal species.

However, a number of scientists have since disagreed with this interpretation.


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You know the scenario: 65 million years ago, a big meteor crash sets off volcanoes galore, dust and smoke fill the air, dinosaurs go belly up.
One theory holds that cold, brought on by the Sun's concealment, is what did them in, but a team of palaeontologists led by Pascal Godefroit, of the Royal Belgian Institute of Natural Sciences in Brussels, argues otherwise. Some dinosaurs were surprisingly good at withstanding near-freezing temperatures, they say.
Witness the team's latest find, a diverse stash of dinosaur fossils laid down just a few million years before the big impact, along what's now the Kakanaut River of northeastern Russia. Even accounting for continental drift, the dinosaurs lived at more than 70 degrees of latitude north, well above the Arctic Circle.

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Dinosaur fossils suggest speedy extinction
Fossils uncovered recently in the Arctic support the idea that dinosaurs died off rapidly - perhaps as the result of a massive meteor hitting Earth. The finding contravenes the idea that dinosaurs were already declining by this time.

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 A U.S. geosciences professor says dinosaurs died gradually from climate change caused by volcanic eruptions in India and not because of a meteor strike.
Gerta Keller of Princeton University admits her theory contradicts the long-held hypothesis that dinosaurs died due to climate change after a giant meteor hit the Yucatan region of Mexico.


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Mass extinctions and the slow rise of dinosaurs
Dinosaurs survived two mass extinctions and 50 million years before taking over the world and dominating ecosystems, according to new research published this week.
Reporting in Biology Letters, Steve Brusatte, Professor Michael Benton, and colleagues at the University of Bristol show that dinosaurs did not proliferate immediately after they originated, but that their rise was a slow and complicated event, and driven by two mass extinctions.

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Excavators working on the high-speed rail link between Madrid and Valencia have uncovered the largest Upper Cretaceous period fossil site in Europe, say Spanish palaeontologists.
More than 8,000 fossils dating back 80 million years - 15 million years before dinosaurs became extinct - have already been removed from a site called Lo Hueco near the village of Fuentes, 15 kilometres from Cuenca.

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DinoSite
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Latitude: 39°56'52.27"N, Longitude: 2° 1'8.33"W

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Dinosaur graveyard may unearth new reasons for their extinction
Spanish scientists have unearthed what could be Europes largest dinosaur boneyard, finding the remains of 65ft plant-eaters never before discovered on the continent. The palaeontologists believe they have found eight different species amid the 8,000 fossils discovered so far.
The range of species they are finding at the 80 million-year-old site and their state of conservation is virtually unparalleled in Europe and challenges long-held beliefs about the way in which dinosaurs became extinct.
Dozens of experts are working around the clock to excavate the site. It was discovered in June during construction work for a new high-speed rail link between Madrid and Valencia. Palaeontologists, who kept the discovery under wraps, have until the end of the month to remove the skeletons of several hundred dinosaurs before the diggers move back in.
Researchers have not finished excavating the entire area of Lo Hueco, near the city of Cuenca, in western Spain. But they say they have retrieved most of the fossils from the path of the railway.
The find is from a period palaeontologists have little information on in Europe. Most of the sites dating from that period have been found in the Americas.

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A worldwide burp of volcanic gases caused the mass extinction that wiped out dinosaurs and other creatures 65 million years ago, says research reported this week. Its the latest argument from a group that has been trying for some time to discredit the leading theory that a meteorite striking Mexico led to the mass die-offs.
The international team says that we should instead blame plumes of climate-altering gas given off by monumental lava flows that stretch hundreds of kilometres across India.
The Deccan Traps, as theyre called, have been suspected before of having some sort of global impact around the end of the Cretaceous period and the beginning of the Tertiary, known as the KT boundary. Earlier research had dated the main outburst of the lava flows as occurring within 800,000 years of the boundary. But the new analysis uses tiny plankton fossils, trapped between lava layers, to date the flow to the boundary itself.


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Did mega-volcanoes kill the dinosaurs?
New evidence dug from the shores of the Bay of Bengal supports the radical idea that it was a series of monumental volcanic eruptions that wiped out the dinosaurs, not a meteor impact in the Gulf of Mexico.
The largest of the massive Deccan traps volcanic eruptions in central India sent basalt lava east across the continent and into the sea.
There, near the town of Rajahmundry, an international team of geologists has found marine fossils deposited immediately on top the largest ancient lava flow there.


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A series of monumental volcanic eruptions in India may have killed the dinosaurs 65 million years ago, not a meteor impact in the Gulf of Mexico. The eruptions, which created the gigantic Deccan Traps lava beds of India, are now the prime suspect in the most famous and persistent palaeontological murder mystery, say scientists who have conducted a slew of new investigations honing down eruption timing.

"It's the first time we can directly link the main phase of the Deccan Traps to the mass extinction" -  Palaeontologist Gerta Keller, Princeton University.

The main phase of the Deccan eruptions spewed 80 percent of the lava which spread out for hundreds of miles. It is calculated to have released ten times more climate altering gases into the atmosphere than the nearly concurrent Chicxulub meteor impact, according to volcanologist Vincent Courtillot from the Physique du Globe de Paris.
Keller's crucial link between the eruption and the mass extinction comes in the form of microscopic marine fossils that are known to have evolved immediately after the mysterious mass extinction event. The same telltale fossilised planktonic foraminifera were found at Rajahmundry near the Bay of Bengal, about 1000 kilometres from the centre of the Deccan Traps near Mumbai. At Rajahmundry there are two lava "traps" containing four layers of lava each. Between the traps are about nine meters of marine sediments. Those sediments just above the lower trap, which was the mammoth main phase, contain the incriminating microfossils.
Keller and her collaborator Thierry Adatte from the University of Neuchatel, Switzerland, are scheduled to present the new findings on Tuesday, 30 October, at the annual meeting of the Geological Society of America in Denver. They will also display a poster on the matter at the meeting on Wednesday, 31 October.

Previous work had first narrowed the Deccan eruption timing to within 800,000 years of the extinction event using palaeomagnetic signatures of Earth's changing magnetic field frozen in minerals that crystallised from the cooling lava. Then radiometric dating of argon and potassium isotopes in minerals narrowed the age to within 300,000 years of the 65-million-year-old Cretaceous-Tertiary (a.k.a. Cretaceous-Palaeogene) boundary, sometimes called the K-T boundary.
The microfossils are far more specific, however, because they demonstrate directly that the biggest phase of the eruption ended right when the aftermath of the mass extinction event began. That sort of clear-cut timing has been a lot tougher to pin down with Chicxulub-related sediments, which predate the mass extinction.

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