Technology Mass Shark Extinction Triggered by Dinosaur-Killing Asteroid

21:34  02 august  2018
21:34  02 august  2018 Source:

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"The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary". " Mass failure of the North Atlantic margin triggered by the Cretaceous-Paleogene bolide impact". ^ "Updated drilling: Dinosaur - killing impact crater explains buried circular hills".

A new scientific model has discovered what actually happened to the earth after the asteroid impact that killed the dinosaurs . This would have shut down photosynthesis, drastically cooled the planet, and contributed to the mass extinction that marked the end of the age of dinosaurs .”

Prehistoric sharks who ate marine reptiles went extinct when their food source also went extinct 66 million years ago. © Illustration by Julius Csotonyi Prehistoric sharks who ate marine reptiles went extinct when their food source also went extinct 66 million years ago. Dinosaurs, birds, and pterosaurs were not the only species to suffer extinctions at the hands of an asteroid that plummeted through the surface of the Earth 66 million years ago. Researchers have found that a mass extinction of sharks followed, wiping out most of what had been the dominant group of these ocean-going predators during the Cretaceous period.

While dinosaurs terrorized the land, giant marine reptiles and a great diversity of sharks patrolled the seas. Some of these sharks, in a group known as the anacoracids, fed on marine molluscs and reptiles, and, as scientists report today in the journal Current Biology, the loss of these prey to the asteroid may have been a contributing factor in their extinction.

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The cataclysmic asteroid that wiped out the dinosaurs might have also triggered massive volcanic It’s yet another way the extraterrestrial impact could have killed off more than 70 percent of life on Earth — that which include wildfires, global cooling, and acid rain — that caused the mass extinction of

How Asteroids Really Killed The Dinosaurs - Part 2 | Last Day Of The Dinosaurs - Продолжительность: 4:29 Your Discovery Science 1 475 645 просмотров. There's A Dinosaur That Survived Mass Extinction !

“Subtle but important shifts may have laid the foundation for what later became the radiation of carcharhiniforms, or ground sharks, which are the most diverse lineage of sharks today,” says study co-author Nicolás Campione, a paleontologist at the University of New England in Armidale, Australia. “After the extinction, carcharhiniforms proliferated… and we hypothesize that changes in food availability played an important role in this shift.”

Shark skeletons are predominantly cartilage, which fossilizes poorly, making the study of ancient sharks difficult. Instead, the international group of authors behind the study looked to something more durable. They analyzed hundreds of shark teeth from fossil deposits left before and after the extinction event to see how the number and shape of teeth changed over time. In very general terms, wide, triangular teeth indicate a cutting function useful for eating large prey, while thinner, longer teeth suggest a grasping function important when eating fish.

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The fact the impact and mass extinction may have been virtually simultaneous in time supports the idea that the cosmic impact dealt the age of dinosaurs its deathblow. Dinosaurs Might Have Survived the Asteroid , Had It Hit Almost Anywhere Else.

San Jose Sharks . About 66 million years ago a 6-mile wide asteroid smacked into Earth, creating the Chicxulub crater in the Yucatan and sparking deadly chaos. Scientists are split, sometimes heatedly, over what really triggered the worst of the extinction , the impact of the crater and its

“This paper makes a strong case for studying sharks and shark fossils as part of the end-Cretaceous extinction,” says William E. Bemis, curator of ichthyology at the Cornell Museum of Vertebrates in Ithaca, New York, who was not one of the study authors.

“Sharks offer a glimpse into changes in marine systems in particular, as groups of marine reptiles went extinct, some to be eventually replaced by marine mammals, while bony fishes explosively radiated,” he says.

There are two major groups of predatory sharks today. Carcharhiniform or ground sharks—including bull, tiger and hammerhead sharks—are the most numerous, represented by more than 250 species. Lamniform or mackerel sharks—such as great white, mako and grey nurse sharks—number only 15 species today.

But during the Cretaceous period this dominance was reversed, with mackerel sharks—in particular, a diverse group of great-white-like species called the anacoracids—being far more numerous than ground sharks. One fearsome and stocky species, Squalicorax, which reached up to 16 feet in length, may have relied on giant marine reptiles for sustenance.

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This led to a mass extinction , which not only claimed the lives of the dinosaurs , but also wiped out about 75% of all land and sea animals on Earth. However, had this asteroid impacted somewhere else on the planet, things could have turned out very differently.

The oceans soured into a deadly sulfuric-acid stew after the huge asteroid impact that wiped out the dinosaurs , a new study suggests. Scientists blame this mass extinction on the asteroid or comet impact that created the Chicxulub crater in the Gulf of Mexico.

Relatively smaller plesiosaurs and mosasaurs, including Plioplatecarpus and Prognathodon, were likely easy pickings for sharks such as Squalicorax. But one of the most common marine reptiles still present at the end of the Cretaceous period was Mosasaurus. At 56 feet long, a full grown Mosasaurus would likely have been too big to be threatened by a Squalicorax. In fact, this apex predator may itself have preyed upon sharks. But Campione says Squalicorax would likely have scavenged dead mosasaurs and hunted juveniles comparable to or smaller than itself in size. Their diet may also have included many large species of squid in coiled shells, known as ammonites.

But when the large prey these mackerel sharks relied upon abruptly vanished after the impact, so too did the sharks that fed upon them. As many as 34 percent of all shark species alive at that time are thought to have died out. Many of the sharks that eventually replaced them were fish-eating species that came to be the ancestors of most of the sharks in our oceans today.

“The end-Cretaceous extinction saw major losses in marine reptiles and cephalopods that would have been an important food source for anacoracids such as Squalicorax,” says Camipone. “The post-extinction world, however, saw the rise of bony fishes. So anacoracids, which would have relied on large marine organisms for sustenance, did poorly across the extinction, whereas predominantly fish-eating forms, such as smaller-bodied houndsharks, did well.”

Rare teeth from ancient mega-shark found on Australia beach

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The asteroid that killed the dinosaurs may have also triggered an intense series of underwater volcano explosions, according The six-mile-wide asteroid crashed into Mexico's Yucatan Peninsula 66 million years ago and precipitated the mass extinction that brought about the end of the dinosaurs .

The asteroid that slammed into the ocean off Mexico 66 million years ago and killed off the dinosaurs probably rang the Earth like a bell, triggering It struck him as more than coincidence that the last four of the six known mass extinctions of life occurred at the same time as one of these massive eruptions.

It's interesting that the overall variety of tooth shapes is similar both before and following recovery from the end-Cretaceous event, comments Michael Coates, an expert on the evolution of fish at the University of Chicago. “As a loose metaphor, the shows goes on, but with a reshuffled cast…. the post-extinction replacements moving into, apparently, much the same eco-space formerly occupied by the extinction victims.”

A fossil tooth from Squalicorax, a fearsome shark which grew up to 16 feet long and went extinct at the end of the Cretaceous period. © Photograph courtesy David Ward, The Natural History Museum A fossil tooth from Squalicorax, a fearsome shark which grew up to 16 feet long and went extinct at the end of the Cretaceous period.

“It's a nice study that adds detail to the emerging picture of how major groups of vertebrates suffered and recovered from the end-Cretaceous mass extinction,” he adds. “Inevitably, this study is limited to the record of shed teeth, shark body fossils being extremely rare. But teeth provide a useful marker of what kinds were present and persisted.”

Through the study of teeth, the researchers were “able to get a glimpse at the lives of extinct sharks,” says Campione. At least 50 percent of living shark species are threatened or declining, so understanding what led to shark extinctions in the past might offer insights into preventing them suffering the same fate, he adds.

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