megalodon: Beast of the Week

This week we're revisiting a VERY popular prehistoric beast that despite its mainstream presence, probably isn't as well understood as lots of people think.  Let's make way for *dunDUn...dunDUN...dundundundundundun...* everyone's favorite giant shark, Otodus megalodon!

Life reconstruction in watercolors of Otodus megalodon by Christopher DiPiazza.

Otodus megalodon (commonly just referred to as its species name, megalodon)  was a gigantic shark that measured over 16 meters (52 feet) long from snout to tail, living from 23 million to as recent as 3.6 million years ago in the Miocene and the Pliocene epochs.  So while this beast never actually was alive at the same time as non-avian dinosaurs, it was around at the same time as primates that were ancestors of modern humans!  (Unless those primates frequently went swimming in the open ocean they would have had nothing to worry about from megalodon, however.) The genus name, Otodus, translates to "ear tooth" because of the shape of the teeth in some members of this genus.  The species name, megalodon, translates to "big tooth" because...look at it.  

As far back as the 1600s, people were finding gigantic triangular fossils and thought they were fossilized tongues from dragons.  Danish scientist, Nicolas Stenos, finally found out they were actually teeth from a gigantic prehistoric shark (just as impressive as a dragon if you ask me).  Since then, megalodon teeth have been discovered on every continent except Antarctica.  Where I currently live in Maryland, there's a site only a bit over an hour's drive from me, in fact, where the public can find their very own megalodon teeth to take home with them.

Nicolas Steno's illustration of megalodon from the 1600s.

 Like all sharks, most of megalodon's skeleton was made of cartilage (same material that is in our noses and ears) instead of bone.  That being said only fossils of its teeth, jaws, and some vertebra have ever been discovered.  Judging by the size of these fossils, however, which includes individual teeth that are almost 18cm (over 7 inches) long, the largest specimens of this shark were estimated to have been almost 16 meters (52 feet) long from nose to tail.  To put it into perspective that's the same size as a modern Humpback Whale.  Even though not much of this shark's actual anatomy is truly known, the teeth themselves are are actually quite common (since sharks tend to shed and replace them a lot).  However, since the teeth and other known elements of this shark are similar in appearance to that of modern Great White Sharks (Carcharodon carcarias) it is possible megalodon could have looked similar to them in life...just a lot bigger.  This being said, megalodon wasn't as closely related to Great Whites as most people think.  In fact, megalodon used to be considered the same genus as Great Whites, Carcharodon, but has since been placed into the genus of extinct sharks, Otodus, instead.  Paleontologists found out that the similarities between megalodon and Great White teeth are likely a result of convergent evolution, not an actual close relationship, and that Great Whites are more closely related to the seemingly different Mako Shark than they are to megalodon.  Great Whites and megalodon appear to have shared a common ancestor much farther back during the Cretaceous period.

Reconstructed mount of megalodon jaws on display at the Baltimore Aquarium in Maryland, USA.

So what was a shark as large as megalodon eating?  Fossil evidence in the form of numerous fossilized whale bones with chew and bite marks on them suggest it was a whale-eater.  It was also likely going after pinnepeds(seals), large fish, and turtles.  Basically megalodon was an opportunistic predator, going after any animal it could overpower, and for an almost 16 meter long shark... that's basically everybody.  This is in part thanks to this shark's incredible biting ability.  It is estimated that an adult megalodon had a bite force between 108,5000 and 182,200 newtons! (24,400 and 41,000lbf)  On top of that power, megalodon's teeth were serrated on the edges, like steak knives, so if it shook its head from side to side after biting, it would have been able to completely slice through fat, muscle, and even bones of large whales.  It is possible megalodon wasn't completely care-free, however, even as an adult.  The similarly sized, and equally monstrous toothed whale, Livyatan lived at the same time and place as megalodon.  These two marine heavyweights were likely competitors and may have also hunted each other depending on which individual was larger than the other in each interaction. 

So why did such a powerful predator go extinct? We may never know for sure but lots of experts feel it may have been a drastic change in environmental temperature that led to its demise.  During megalodon's time on earth, geological activity led to a decrease in global temperature which diminished tropical waters a large shark would thrive in.  A shark like megalodon likely didn't have the adaptations to deal with cooler temperatures, especially at such a large size.  Many modern sharks give birth in shallower, warmer waters, called nurseries.  If megalodon did the same but on a larger scale, there is a chance this climate change event could have eliminated whatever specific places it was using to reproduce, thus also leading to its extinction.  

Lastly I feel it is important to note that despite what you may hear on certain television shows, megalodon is most certainly gone forever.  It's definitely not still out there in the deepest parts of the ocean hiding somewhere.  We know this prehistoric predator was hunting whales in life.  Whales often hang out near the ocean's surface.  We'd see a megalodon by this point if any were still alive.  I'm not sure where the idea of this beast as a cryptid came from, but it's most definitely not based on anything credible.  

Works Cited

Augilera, Orangel A.; García, Luis; Cozzuol, Mario A. (2008). "Giant-toothed white sharks and cetacean trophic interaction from the Pliocene Caribbean Paraguaná Formation". Paläontologische Zeitschrift. 82 (2): 204–208. 

Bruner, J. C. (Sept.-Oct. 1997). "The Megatooth shark, Carcharodon megalodon: Rough toothed, huge toothed". Mundo Marino Revista Internacional de Vida (non-refereed) (Marina) 5: 6–11

Collareta, A.; Lambert, O.; Landini, W.; Di Celma, C.; Malinverno, E.; Varas-Malca, R.; Urbina, M.; Bianucci, G. (2017). "Did the giant extinct shark Carcharocles megalodontarget small prey? Bite marks on marine mammal remains from the late Miocene of Peru". Palaeogeography, Palaeoclimatology, Palaeoecology. 469: 84–91. 

Haven, Kendall (1997). 100 Greatest Science Discoveries of All Time. Libraries Unlimited. pp. 25–26. ISBN 1-59158-265-2.

Pimiento, Catalina; Dana J. Ehret, Bruce J. MacFadden, and Gordon Hubbell (May 10, 2010). Stepanova, Anna. ed. "Ancient Nursery Area for the Extinct Giant Shark Megalodon from the Miocene of Panama"

Wroe, S.; Huber, D. R.; Lowry, M.; McHenry, C.; Moreno, K.; Clausen, P.; Ferrara, T. L.; Cunningham, E.; Dean, M. N.; Summers, A. P. (2008). "Three-dimensional computer analysis of white shark jaw mechanics: how hard can a great white bite?". Journal of Zoology. 276 (4): 336–342.