Thirty-three years ago a young upstart director named Steven Speilberg made what is now viewed as the first summer blockbuster movie. This film made stars of Richard Dreyfuss, Roy Scheider and Robert Shaw, who played the fantastic trio of characters named Hooper, Brody and Quint. But the real star was "Bruce", the mechanical fish named after Speilberg’s lawyer, whose job it was to bring to life Peter Benchley’s killer great white shark that terrorized the fictional town of Amity, New York.
This film changed the way the world looked at sharks. For many people the very thought of going swimming in the ocean again was terrifying. For an eight-year old in Rhode Island named Mark H, that movie was mesmerizing and possibly did more to cement my future profession than anything else in my life. Sitting with my dad at the Lincoln Mall cinema number two, twelfth row, five seats in from the left, I had a feeling of both elation and dread. (I can remember the cinema, row and seat number I was in for every movie I’ve ever seen in my life. Go figure.) Even at this young age I could sense a genocide of sorts brewing. My fears were realized as newspapers and newscasts became obsessed with reporting shark attacks and shark catches. Marinas in my town held shark derbies, with the winning anglers posing with their catches. And for a while it was the great whites that bore the brunt of this obsession.
Life-size model of a megalodon jaw.
In recent years I sense the feeling toward sharks has gone from fear to respect, thanks in part I’m sure to the explosion of nature shows on cable tv in the past twenty years. Still, a twenty foot long fish with razor sharp teeth and a top swimming speed of thirty miles per hour is pretty intimidating. Now imagine if this shark was closer to fifty feet in length.
Megalodon has been extinct for at least five million years. Because of the similarity between fossilized teeth and those of modern great whites, the two are classified by taxonomists as being two species within the genus Carcharodon. Great whites are C. carcharius and the extinct monster is C. megalodon. It was widely believed that megalodon was actually an ancestor of today’s white sharks. This belief is now disputed and the two species may in fact be unrelated, with the similarities due to a case of convergent evolution. Convergence occurs when similar traits arise independently in two unrelated organisms.
Magalodon tooth compared to modern
great white shark tooth.
Pretty much everything we know about the megalodon is based on fossilized teeth. Because a shark’s skeleton is made up of cartilage rather than bone, other structures are difficult to find. Estimates on the size of this fish, as well as other characteristics, must be inferred based on these teeth and the comparative anatomy of living sharks.
The megalodon is assumed to have been a pelagic predator that occurred throughout the world, based on fossilized teeth being found on every continent except Antarctica. Because a shark the size of megalodon would need to eat nearly 1500 pounds of food per day to sustain its fifty-ton body, the hunting proficiency must have been pretty spectacular. Its main diet probably consisted mainly of whale ancestors and other warm-blooded mammals. Not only are the teeth huge, but they are nastily serrated, ideal tools for cutting and shredding bite-sized chunks out of a large prey.
Like today’s large species of sharks, megalodon most likely hunted using an initial powerful ambush attack to wound the prey, followed by a circle-and-wait phase while the victim bleeds and weakens. Because some fossilized whale bones have been found with megalodon teethmarks on the tail and flippers, this fish probably attacked a large prey by first inflicting damage on its ability to swim.
After 14 million years of dominating the seas worldwide, megalodon suddenly became extinct during the end of the Pliocene epoch. Its extinction probably occurred because of both climate change, as the oceans did cool off during this period, as well as the disappearance of its prey. Several species of marine mammals, such as the walrus-toothed whale, also became extinct around the same time, while evidence suggests that others adapted to the colder polar seas for at least part of the year. I would imagine that the loss of key prey species would make such a large predator very susceptible to no longer being able to get the calories it needed to sustain its metabolism.
Although there have been rumors over the years that megalodon could possibly still be alive as a relic species, these are assuredly just myths left to the pseudoscience of cryptozoology. Still, the thought of what may be earth’s most fearsome predator lurking in the depths is pretty powerful.
Megalodon tooth photo by Kossack Jason.
Other diaries in this series can be found here.
[Update:] If you missed my entry on shark finning, that diary is here.