Brocken Inaglory, Wikimedia Commons
This comparison shows how large Megalodon teeth were compared with those of living great white sharks.
Karen Carr, Wikimedia Commons
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 (
) became extinct much later, with some even believing that the enormous shark never did die out. "I was drawn to the study of
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
Walter Voigt/Lee Berger/Brett Hilton-Barber
If megalodon did indeed become extinct 2.6 million years ago, then members of our genus
were not around when the huge shark was still alive. Human-like beings were in existence, however, such as members of the genus
, shown here. Many other terrestrial animals also existed, as did birds, plants and insects.Photos: Faces of Our Ancestors
Jason Bourque, Florida Museum of Natural History
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
"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?
Dmitry Bogdanov, Wikimedia Commons
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
— aka Terror Bird — were formidable in their own habitats. Terror Bird is thought to have stood 8-feet-tall and weighed over 300 pounds.
Ehret and other paleontologists believe that megalodon frequently feasted on whales. One such species was
, 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
Joachim Huber, Wikimedia Commons
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.
U.S. Fish and Wildlife Service Southeast Region
Leatherback sea turtles are the only living species in the genus
. 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
Dmitry Bogdanov, Wikimedia Commons
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.
Liam Quinn, Wikimedia Commons
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
Whit Welles, Wikimedia Commons
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
The largest known shark known to have lived, Megalodon, had teeth that were unlike those of any living animal, according to new research.
Large and powerful Megalodon, which grew up to 66 feet long, flashed teeth that were heavily comprised of fluoride, the new study determined. Modern sharks only have fluoride on the surface, or enamel, of their teeth. The findings are published in the journal RSC Advances.
“You might say that they also used ‘built-in toothpaste,’” senior author Matthias Epple, a professor at the University of Duisburg-Essen’s Institute of Inorganic Chemistry, told Discovery News.
“The ‘built-in toothpaste’ refers to the fluoride content,” he said, adding that Megalodon never suffered from cavities.
This, however, was primarily because the enormous shark had a “revolving jaw” that regularly replaced any teeth that went missing, maybe left behind in prey. Today’s great whites and other sharks benefit from such a replacement system too.
Megalodon teeth were almost 8 inches long, making them much larger than those of any living shark. Now extinct, Megalodon is thought to have terrorized ocean dwellers from around 16 to 2 million years ago.
For the study, Epple and his colleagues compared Megalodon teeth with teeth from five other extinct shark species, three living sharks (great white, tiger and mako), as well as teeth from two extinct marine reptiles and two dinosaurs: Spinosaurus marocannus (“Spine Lizard”) and Carcharodontosaurus saharicus. Both of the dinosaurs were large carnivores.
The researchers focused on the chemical composition and microstructure of the teeth from these animals and determined that the now-extinct sharks and dinosaurs had fluoride on and within both the surface and interiors (dentin) of their teeth. This unique chemical composition occurred in these animals and related species for more than 100 million years.
A few million years ago, sharks evolved teeth that only had fluorapatite (the mineral associated with the compound fluoride) on the surface. The dentin mineral is now primarily hydroxyapatite, which comprises about 96 percent of human tooth enamel.
Why the switch happened remains a mystery, but Epple and his team suspect that fluorapatite must have been more common in prehistoric times than it is today. He explained that now “fluoride is not very common in seawater, (so) it is difficult for animals to collect fluoride, especially for a revolving jaw in sharks where the teeth are replaced every few weeks or months.”
According to a University of California at Santa Barbara fact sheet, “Fluorapatite is more resistant to decay than is hydroxyapatite.” Epple also said that “fluoroapatite as a mineral is slightly harder than hydroxyapatite.”
That could be that Megalodon and the other prehistoric animals had sturdier teeth than any living creature today.
On the other hand, Epple said that fluorapatite releases a damaging acid -- hydrofluoric acid -- on contact with acidic fruits and certain other edibles, like meat, which are found on land.
He does not think dinosaurs suffered from tooth decay much, though.
“They used fluoride in teeth for several millions of years without apparent problems,” he said, adding that the carnivorous dinosaurs that he and his colleagues studied probably rarely, if ever, ate fruit.
Diet also helps to explain why humans did not evolve continuously replacing teeth, like those of sharks.
Barry Berkovitz of King’s College London’s School of Biomedical Sciences, explained, “Continuous tooth replacement is particularly inefficient in mammals where teeth bite together to masticate food. They have evolved different strategies to cope with having only two sets of teeth during their lives.”
He added, “In humans, the ultimate solution is to get a third set from the dentist!”