Why did megalodon shark become extinct

For twenty million years, the world's oceans were home to a monstrous shark, named the 'megalodon'. Then suddenly, without explanation, the metre-long 50 foot super predator disappeared.

It's a juicy bit of ancient history that has inspired a host of books, documentaries and blockbuster films, some of which like to imagine that this bloody thirsty monster is still alive today, lurking somewhere out there in the mysterious deep. A new study has once again confirmed that this is not the case. Taking a fresh look at the fossil record, researchers are now proposing that this mega marine creature may have been killed off by none other than the modern great white shark Carcharodon carcharias.

The timing is everything. They quickly expanded their search to other regions, to take a broader look at this ancient disappearing act. The samples in their growing list were not only ones the researchers found themselves, but also fossils from the published literature and freshly scrutinized discoveries in museum collections. Several times throughout this hunt, the team tried to publish their work.

And though reviews were generally positive, Boesenecker says, there always seemed to be a reason for rejection, including concerns about the paper's length the final version is 47 pages, not counting appendices. Still, they weren't the only ones hunting for clues. In , Catalina Pimiento of the University of Florida and Christopher Clements of the University of Zurich published their analysis of the megalodon's extinction using available records.

That team concluded that these creatures could have lingered in the oceans until sometime around 2. For the latest study, Boessenecker and his colleagues combined their sleuthing with the study's data into one mega-catalog. But they were suspicious of some of the more recently described teeth and vertebrae. Some samples were broken or chemically altered by the element phosphorus—evidence that they hadn't stayed put through the millennia and could be feigning a younger age.

Others seemed to have iffy origins, making it impossible to accurately position them in time. Still others needed date readjustments that took more recent analyses of those samples into account. Boessenecker estimates that they excluded 10 to 15 percent of the samples that lacked the necessary exactness in space and time.

And as they pored through the remaining records one by one, a pattern started to emerge. She agrees with the exclusion of some of the samples, particularly ones whose physical positions shifted over time, or ones that had uncertain origins.

But she doesn't necessarily agree with excluding samples that have a wide range of possible ages. Getting a more accurate read on the megalodon's demise is vital for understanding the forces driving the disappearance of these mega-beasts. Past theories were often tied to a wider marine extinction that happened as the curtains closed on the Pliocene epoch roughly 2. Before this change, the waters were full of relative oddballs: toothless walruses, aquatic sloths, dwarf baleen whales, and more.

Some 36 percent of early marine genera didn't make it to the next epoch, Pimiento and her colleagues estimate in a study. Afterward, a more modern menagerie began to appear.

Some astronomers have suggested the die-out was tied to a supernova that enveloped the planet in harmful muon radiation. But Pimiento and Boessenecker both emphasize that the extinction event could have been a much slower-moving affair, and many factors were likely at play.

For one, Earth was going through a mighty flux during this time frame, Pimiento says. The world was cooling, so glaciers were expanding and sea levels were dropping, transforming available ocean space. The reasons for its demise, as well as whether the creature might still be hiding in the depths of the ocean, are under constant debate. Because shark skeletons are made of cartilage, usually all that survives decomposition is the teeth. Based on the size of Megalodon teeth, which have been found measuring up to 7 inches in height and weighing over a pound, scientists have determined this shark could have been 50 feet long and weighed around 50 tons.

Megalodons appeared during the mid-Miocene period, roughly 16 million years ago. They are believed to have gone extinct in the Plio-Pleistocene period about 1.

Gradually, mid-latitude temperature saw a decrease of roughly 15 degrees Celsius or 27 degrees Fahrenheit.

Because Megalodon teeth have been found in mostly warmer waters, it may not have tolerated the cooler temperatures. The super continent Pangea was breaking up, eventually resulting in the familiar continents we have now. The Isthmus of Panama broke the surface of the sea between 7 million and 3 million years ago.