Carcharodon megalodon, the megatooth shark, isn't just a favorite topic among science fiction fans and cryptozoologists (who study evidence of the existence of unverified species) -- it was a real, living shark that roamed the oceans around 1.5 to 20 million years ago. C. megalodon was discovered in the 1600s when naturalist Nicolaus Steno identified large fossils -- previously thought to be tongues of dragons or snakes -- as giant shark teeth. Since then, biologists and scientists have unearthed hundreds of fossilized megalodon teeth and centra (boney, vertebraelike spinal segments), allowing us to learn more about this mysterious creature of the ancient seas.
Popular sci-fi books and films continue to elevate the megalodon to mega pop culture status. Some have even fueled myths that perpetuate the belief that this giant shark lived during the same time as dinosaurs (though they went extinct some 45 million years before megalodon existed) or humans (though we've only been around for about 100,000 years).
In addition to confusion over when megalodon existed, some fanatics believe this supersized beast isn't extinct at all, but is still lurking in our oceans. Is it really possible for a creature of mega-proportions to live without detection for millions of years? And just how big was megalodon anyway? In this article, we'll answer these questions and delve into what life might have been like for megalodon -- along with what makes this mystery monster such a hot topic today. It all begins on the next page with megalodon's above-average anatomy.
Since the skeleton of a shark is primarily made up of cartilage, which disintegrates over time, the only megalodon remains we've discovered are serrated teeth and vertebraelike centra. This has left experts with the arduous task of reconstructing megalodon's anatomy based on limited knowledge. But, just as human dental records can be examined postmortem to identify remains, shark teeth can also tell experts enough to identify the species and its size, possible prey, and prey size. Hundreds of megalodon tooth fossils have been found, and they average 6 inches (15 centimeters) in length -- about the size of a human hand. By comparison, great white sharks' teeth average around 2 inches (5 centimeters) long.
Using fossilized teeth, scientists have reconstructed the jaws of the megalodon and discovered that this shark's mouth was a staggering 7 feet (2 meters) in diameter. Based on this reconstruction and additional research, experts believe that this ancient shark had a broad, domed head with a short snout and massive jaws. If the latest reconstruction is accurate, paleontologists believe megalodon was wider than the great white with larger pectoral fins, and could have grown up to 45 to 60 feet (13.7 to 18.2 meters) in length -- about the size of a Greyhound bus.
In addition to the knowledge gained from megalodon teeth, the centra tell their own story. Because sharks are cold-blooded, each year they get growth rings on their vertebrae with the changing of the seasons, just as a living tree does. Experts can easily determine a megalodon's age at death by examining the centra and counting how many rings appear. The color and width of the rings also help determine growth rate; wide, light rings indicate a faster growth than narrow, dark rings. By studying megalodon's tendencies in growth rate and age at death, scientists are able to understand more about sharks' evolution and how to conserve today's shark populations, too.
Life of a Megalodon
What could life have been like for such a monolith of the sea? Many theories float around about the megalodon's habitat and prey. Megalodon fossils have been discovered far and wide, from Japan to the United States, so researchers conclude that megalodon was an intercontinental species, living all over the world's ancient oceans. Due to the coastal locations where the most fossils have been discovered, experts believe the megatooth shark had similar habitats as the great white of today -- living offshore in more temperate climates and setting up nurseries in warm, shallow water closer to coastlines [source: Renz].
In 2009, a group of paleontologists from the University of Florida in Gainesville discovered the fossilized remains of a megalodon nursery in Panama that was made up almost entirely of juvenile megalodon tooth fossils. Between this new discovery and a breeding ground found in South Carolina, scientists believe that an infant megalodon could have been an average 20 feet (6 meters) long, the same size as an adult great white.
Because of its sheer size, this species was the top predator of its time and would have needed to eat a lot to survive. Experts estimate that the average adult female weighed between 50 to 100 tons (45 to 90 metric tons -- about the size of half of a blue whale) and could eat up to 2,500 pounds (1,136 kilograms) of food per day. That's over 500 pounds (227 kilograms) more than the average American eats in an entire year.
Life at the top of the food chain meant the megalodon could eat whatever it wanted, and with its supersized, serrated teeth and a wide mouth, it could disable whales and seals easily before gulping them down. A team of researchers in Australia determined the megalodon's bite force was so strong, it could crush the skull of a whale as easily as a human can eat a grape [source: Wroe]. So what happened to the megatooth shark that knocked it from the top of the food chain to complete extinction? Find out on the next page.
Extinct Legend or Living Myth?
Most scientists, paleontologists and other experts believe from the fossil evidence that megalodon became extinct over 2 million years ago during the Plio-Pleistocene period, but some cryptozoologists and researchers think that this giant shark may still exist in the undiscovered depths of the ocean. For those who accept megalodon's extinction, one theory puts changes in climate and shifts in the continents as the cause. Another suggests that that large predators like orcas and great whites could have preyed on juvenile megalodons, decreasing their chance for survival to adulthood. Megalodon expert Gordon Hubbell theorizes that the megalodon's diminishing food sources could have also been responsible for its demise -- as whale populations disappeared from tropical waters, the megalodon began to disappear, too.
Proponents of the theory of megalodon's continued existence often point to eyewitness accounts to debate the possibility of the species' survival. Occasionally, a report will surface about a large, unidentified shark in the ocean, but those accounts have been mostly discounted as tall tales. Some researchers say that the discovery of new, unfossilized teeth proves that megalodon lives, but zoologist and cryptozoology expert Ben Speers-Roesch explains that these reports are erroneous and ignore the fact that no truly unfossilized teeth have ever belonged to megalodon.
Some cryptozoologists also use examples of other recent discoveries of new species as a final point in this debate, citing the discovery of the deep-sea megamouth shark (Megachasma pelagios) in 1976. While new discoveries like the megamouth do show that we have yet to explore all that our oceans hold, scientists say it's difficult to draw a comparison from marine animals that live in the depths of the ocean and generally feed on plankton to the coastal megalodon, which was a carnivore, not a planktivore. Most scientists agree a shark of this magnitude would most certainly have been discovered by now if it were still living in its natural habitat.
The Modern Megalodon
Despite the fact that scientists believe megalodon has been extinct for 1.5 to 2 million years, this mysterious megabeast continues to fascinate and educate people today. As we mentioned before, it's important to understand megalodon's history, because it provides clues about the evolution of sharks and can help with today's shark conservation efforts. Since several shark species are showing signs of population decline, scientists look to megalodon to help them understand how a top marine predator can become extinct. Sharks may have a reputation for being killers, but they provide a vital service in ocean ecosystems by keeping carnivorous fish populations down.
The megalodon's only legacy isn't marine conservation, though; it has become a pop culture phenomenon among science fiction fans who gobble up anything related to the megatooth shark. The New York Times best-selling author Steve Alten wrote a series of books called "Meg" that depicts the megalodon terrorizing humans and dinosaurs -- neither of which actually existed at the same time as megalodon. But these inaccuracies proved to be the right combination for fans, and although "Meg" has yet to make an appearance on the silver screen, schlocky thrillers about giant sharks have become television and DVD hits.
When the trailer for "Mega-Shark vs Giant Octopus" was released online in May 2009, it became an instant hit on MTV.com and YouTube, thanks in part to '80s pop queen Debbie Gibson starring in the lead role. Despite getting a negative rating on the movie review Web site Rotten Tomatoes, the megalodon proved that it's too big to fail as this direct-to-DVD film went on to become a cult classic. In December 2010, the sequel -- "Mega Shark vs Crocosaurus," starring Jaleel White -- was released to even worse reviews, but television networks continue to explore the mysterious megalodon. Discovery Channel and History Channel have explored the megalodon in shows like "Prehistoric Sharks" and "MonsterQuest."
The megalodon may be extinct, but the mega-obsessed will continue to search out anything related to this mysterious sea creature, and some collectors will pay top dollar for a rare megalodon tooth. It's not uncommon to find megalodon teeth up for auction on eBay, and some have sold for up to $1,500.
The Mexican grizzly bear is presumed extinct, and the reason for its demise is pretty unfortunate. Learn more about its extinction at HowStuffWorks.
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