Shark Files: Tiger Sharks Make Astonishing Journeys
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Controversy has surrounded the timetable of existence for megalodon, the world's largest ever shark, but a new study concludes that this 60-foot-long predator became extinct 2.6 million years ago.
Giant Shark, Megalodon, Had Lots of Company: Photos
Controversy has surrounded the timetable of existence for megalodon, the world's largest ever shark, but a new study concludes that this 60-foot-long predator became extinct 2.6 million years ago. The study, published in the latest issue of the journal PLOS ONE, counters other theories that megalodon ( Carcharocles megalodon ) became extinct much later, with some even believing that the enormous shark never did die out. "I was drawn to the study of Carcharocles megalodon's extinction because it is fundamental to know when species became extinct to then begin to understand the causes and consequences of such an event," explained lead author Catalina Pimiento. Three Deadliest Sharks Named
Karen Carr, Wikimedia Commons
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If megalodon did indeed become extinct 2.6 million years ago, then members of our genus Homo were not around when the huge shark was still alive. Human-like beings were in existence, however, such as members of the genus Paranthropus , shown here. Many other terrestrial animals also existed, as did birds, plants and insects. Photos: Faces of Our Ancestors
Walter Voigt/Lee Berger/Brett Hilton-Barber
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While not as large as monstrous megalodon, other big sharks lived at the same time. Dana Ehret, curator of paleontology for the Alabama Museum of Natural History, told Discovery News that Carcharodon sp. "most likely shared habitat" with megalodon. It belonged to the same genus as today's great white sharks and was just as fierce. Shark-Eat-Shark: Are Great White Sharks Cannibals?
Jason Bourque, Florida Museum of Natural History
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Non-avian dinosaurs were long gone by the time megalodon emerged, as they all died out 66.5 million years ago. Many of their bird relatives, however, were going strong during megalodon's lifetime. Some, including Titanis walleri — aka Terror Bird — were formidable in their own habitats. Terror Bird is thought to have stood 8-feet-tall and weighed over 300 pounds.
Dmitry Bogdanov, Wikimedia Commons
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Ehret and other paleontologists believe that megalodon frequently feasted on whales. One such species was Squalodon calvertensis , shown here. Megalodon is thought to have emerged approximately 17 million years ago, while Squalodon went extinct around 14 million years ago. Was the whale's entire population eaten to death over time? That has not been ruled out, although researchers have also proposed competition from dolphins and climate change as other possible reasons for the whale's extinction. Video: Whale Attacked by Megalodon
Nobu Tamura
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Evidence suggests that seals have been on Earth for at least 15 million years. Ehret said that they would have been in megalodon's habitat. Seals likely served as meaty snacks for megalodon.
Joachim Huber, Wikimedia Commons
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Leatherback sea turtles are the only living species in the genus Dermochelys . Many other members of this genus existed in years past, however, including giant sea turtles during megalodon's time. Could megalodon have bitten through their hard shells? The answer is probably not, based on modern great white shark bite force measurements and behavior. Megalodon's teeth were nonetheless formidable. Ehret said that the teeth were "much different" than those of other sharks during megalodon's lifetime, "having much finer serrations, being much thicker, and possessing a 'chevron,’ which is a V-shaped portion of the tooth crown." Leatherback Turtles Wear Tracking Backpacks
U.S. Fish and Wildlife Service Southeast Region
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Large, plant-loving Desmostylus was a hippo-like animal that lived during the earlier part of megalodon's time on the planet. Comfortable both on land and in water, Desmostylus surely would have attempted a hasty getaway if megalodon were near. Desmostylus usually ventured in freshwater, though, seeking aquatic plants.
Dmitry Bogdanov, Wikimedia Commons
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The first penguins are thought to have emerged around the time of the mass extinction event 66.5 million years ago that ended the Cretaceous Period. Ehret said penguins would have shared habitat with megalodon. Some prehistoric penguins grew to be quite large, such as "Colossus," which stood 6'7" tall. It preceded megalodon's existence, however. The penguins during the large shark's lifetime would have been like a kernel of popcorn to megalodon, which probably exerted more effort targeting much larger prey. Extinct Penguin Was Tall Enough to Play in the NBA
Liam Quinn, Wikimedia Commons
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When one animal goes extinct, the void can really benefit other species. Dinosaur extinction, for example, benefitted mammals, which evolved to become the world's dominant animals. Pimiento similarly believes that megalodon's demise led to bigger whales. "When we calculated the time of megalodon's extinction, we noticed that the modern function and gigantic sizes of filter feeder whales became established around that time," Pimiento said. "Future research will investigate if megalodon's extinction played a part in the evolution of these new classes of whales." Blue Whales Keep Getting Bigger
Whit Welles, Wikimedia Commons
Tiger sharks really get around, travelling over 4,500 miles between the warm waters of the Caribbean and the cold North Atlantic, CBS News reported.
One tiger shark travelled over 27,000 miles, longer than any other shark recorded, a study in the most recent Scientific Reports said.
James Lea of Nova Southeastern University’s Guy Harvey Research Institute in Florida, who was part of the study, told CBS News that the journeys, which happen year in and year out, “were very unexpected.”
Tiger sharks have always been thought to be a species that hugs the coastlines, and so it’s unusual to see the sharks switching between such different environments, Lea said.
Researchers tagged tiger sharks near Bermuda. The tags transmit data every time the sharks surface, and these tags were winners, some staying with the shark for three years.
That let the shark scientists see that these long journeys weren’t one-offs; they happened year after year, a bit like retirees flocking south for the winter.
As for why the sharks switch out environments, the researchers speculate that they’re chasing food.
“There’s got to be something really good up there to make the sharks undertake such massive, repeated swims, but exactly what is a puzzle,” Mahmood Shivji, who was also part of the study, told CBS News.
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