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Comet May Have Hit Earth 56 Million Years Ago, Triggered warm, ice-free period on Earth: Scientists

The researchers said they have not found the location of an impact crater linked to the collision

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A tiny sand-grain-size tektite, thought to be created when vaporized material from an impact solidified while flying through the air, is shown in this image released in New York, Oct. 13, 2016. VOA
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October 14, 2016: Droplets of glass dug up in New Jersey and from the Atlantic seabed indicate a comet or some other extraterrestrial object may have smacked Earth 56 million years ago, roughly 10 million years after the asteroid impact that doomed the dinosaurs.

Scientists said on Thursday the collision may have triggered a particularly warm, ice-free period on Earth when important mammalian groups, including the primate lineage that led to humans, appeared for the first time.

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The findings, published in the journal Science, marked the latest evidence of the profound influence that past impacts by celestial bodies have had on life on Earth.

The tiny spherical bits of dark glass, called microtektites, represent strong evidence of a collision with a comet or asteroid, the researchers said. They form when a space rock hits Earth’s surface and vaporises the spot where it lands, ejecting into the air bits of molten rock that solidify into glass.

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The microtektites were excavated from a geological layer marking the start of the Eocene Epoch about 56 million years ago from three sites in southern New Jersey (Millville, Wilson Lake and Medford) and an underwater site east of Florida.

That coincided with the beginning of a warming event, called the Paleocene-Eocene Thermal Maximum, associated with an accumulation of atmospheric carbon dioxide. It lasted more than 100,000 years and drove up global temperatures about 9-14 degrees Fahrenheit (5-8 degrees Celsius).

The impact of an asteroid about six miles wide (10 km) off Mexico’s Yucatan Peninsula 10 million years earlier killed off many marine and terrestrial creatures including the dinosaurs, and enabled mammals to gain supremacy.

No such mass extinction was associated with the event 56 million years ago, although many single-celled ocean-bottom creatures disappeared. During the warming period, primates and two mammal groups — one that includes deer, antelope, sheep and goats and another that includes horses and rhinos — first appear in the fossil record.

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The researchers said they have not found the location of an impact crater linked to the collision. They said geological evidence suggested the object was a comet.

“We can’t really say where it was, or how big, at this point,” said geochemist Morgan Schaller of Rensselaer Polytechnic Institute, who led the study.

While the findings are not proof that the impact caused the warming period, they are “a rather dramatic finding in support of an impact trigger” for the climate changes, said planetary scientist Dennis Kent of Columbia University’s Lamont-Doherty Earth Observatory and Rutgers University. (VOA)

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Palaeontologists Find Similarities Between Ancient Dinosaurs And Birds

The new Alvarezsaurian dinosaurs are among the most bizarre groups of theropods, with extremely short, robust forelimbs with a single functional claw and gracile, bird-like skulls and hind limbs.

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Dinosaurs' faces
Dinosaur. Wikimedia

An international team of palaeontologists have found how a meat-eating species of dinosaurs, that share many similarities with birds, lost their fingers.

The fossil specimens of “Xiyunykus pengi” and “Bannykus wulatensis”, discovered in China, are an enigmatic group of theropods known as alvarezsaurs.

Their bodies were found to be slender, with a bird-like skull and many small teeth instead of the usual large, sharp cutting teeth of their meat-eating relatives.

“Alvarezsaurs are weird animals. With their strong, clawed hands and weak jaws, they appear to be the dinosaurian analogue to today’s aardvarks and anteaters,” said Jonah Choiniere, Associate Professor at the Wits University in South Africa.

Fossils, dinosaurs
Fossils. Pixabay.

However, “the new fossils have long arms and show that alvarezsaurs evolved short arms only later in their evolutionary history, in species with small body sizes. This is quite different to what happens in the classic example of tyrannosaurs, which have short arms and giant size,” said co-author Professor Roger Benson from Britain’s Oxford University.

According to the researchers, the alvarezsaurs did not always look this way. Early members of the group had relatively long arms with strong-clawed hands and typical meat-eating teeth. Over time, they evolved into dinosaurs with mole-like arms and a single claw.

Bannykus and Xiyunykus are important because they show transitional steps in the process of alvarezsaurs adapting to new diets, the researchers said, in the paper published in the journal Current Biology.

The new Alvarezsaurian dinosaurs are among the most bizarre groups of theropods, with extremely short, robust forelimbs with a single functional claw and gracile, bird-like skulls and hind limbs.

Also Read: Fossils of 400 Year Old Invertebrate Marine Species Found in China

These specialisations have led to a controversy about their phylogenetic placement, biogeographic history and ecological role in Mesozoic ecosystems, the team notes. (IANS)