Megalodon: Scientists Reveal a Crucial Surprise About The Mega-Shark
It remains a sad fact of this world that we will never know for certain what the long-lost megalodon truly looked like – but a new study gives us what may be the most accurate reconstruction yet.
An international team led by paleontologist Kenshu Shimada of DePaul University in the US has determined that the megalodon (Odontus megalodon) was probably longer and sleeker than previous interpretations of its scant, mysterious remains.
"This study provides the most robust analysis yet of megalodon's body size and shape," says marine biologist Phillip Sternes, formerly of the University of California Riverside, now at SeaWorld.
"Rather than resembling an oversized great white shark, it was actually more like an enormous lemon shark, with a more slender, elongated body. That shape makes a lot more sense for moving efficiently through water."
The megalodon is one of the most captivating mysteries on the fossil record. It lived from around 23 million to around 3.6 million years ago, during which time it occupied a prime position at the top of the food web, before being driven to extinction.
We know it was huge, compared to modern sharks, but learning more about what it looked like is extremely difficult. That's because, like those of today's sharks, megalodon's skeleton was mostly cartilage.
Only its teeth and vertebrae have been preserved as fossils on the seafloor, indicating a monster of a shark that could have been anywhere between around 11 meters to over 40 meters (36 to 131 feet) in length.
Most estimates settle between around 13 to 18 meters, with the white shark (Carcharodon carcharias) as the basis for their model, using one of the most complete megalodon fossils we have: an almost complete spine found near Belgium measuring 11 meters in length.
The white shark is a true powerhouse, one of the fiercest predators in the ocean, so it's easy to see why scientists might turn to it to understand the megalodon. Not all sharks are built alike, though.
Rather than examining the megalodon spine in the context of just a handful of species, Shimada and his colleagues compared it against a huge catalog of 145 living and 20 extinct shark species.
In particular, they were looking to calculate the length of the body parts not represented by the fossilized vertebral column; that is, the head and the tail of the shark.
Their new approach found that if the megalodon's body plan was consistent with most of the other sharks evolution has so elegantly crafted, the extinct predator's head and tail could have represented 16.6 and 32.6 percent of the total body length, respectively, with a sleeker, slimmer body more like that of the lemon shark (Negaprion brevirostris) than the white shark.
This means that, for the Belgian individual, the head would have measured 1.8 meters in length and the tail 3.6 meters, making that specific megalodon a total of 16.4 meters wide.
Although the Belgian spinal column gives scientists a bunch of related bones to work with, they are not the only megalodon vertebrae paleontologists have found; nor are they the largest. The largest vertebra in the assemblage is 15.5 centimeters (6.5 inches) long.
Other vertebrae found near Denmark are reported to be significantly larger, up to 23 centimeters across. Assuming that this represents the largest possible size a megalodon vertebra can reach, the researchers calculated a new top size for the shark.
"The length of 24.3 meters is currently the largest possible reasonable estimate for O. megalodon that can be justified based on science and the present fossil record," Shimada says.
That length is comparable to two school buses, end-to-end, much larger than most sharks that swim the oceans today, although filter-feeding whale sharks (Rhincodon typus) can reach lengths of 20 meters or so, and actual whales can be significantly larger.
The interesting thing about all these large marine animals is that their bodies, also, are long and sleek. The shorter, stockier shape of the white shark is built for short bursts of speed; the longer, sleeker bodies of lemon sharks, whale sharks, and whales are better for more energy-efficient swimming, and minimal drag.
A longer, sleeker, more hydrodynamic body would have allowed megalodon to grow much larger than the white shark, whose maximum body size is less than 6 meters, limited by the energy demands of its swimming and hunting style.
At 23.4 meters in length, a megalodon would have cruised the oceans at speeds around 2.1 to 3.5 kilometers (1.3 to 2.2 miles) per hour, using sparing speed bursts only when necessary.
"This research not only refines our understanding of what megalodon looked like, but it also provides a framework for studying how size influences movement in marine animals," Sternes says.
"Gigantism isn't just about getting bigger – it's about evolving the right body to survive at that scale. And megalodon may have been one of the most extreme examples of that."
The research has been published in Palaeontologia Electronica.
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