The megalodon, scientifically known as Otodus megalodon, is an extinct species of giant mackerel shark that lived approximately 23 to 3.6 million years ago, from the Early Miocene to the Early Pliocene epochs. Commonly known as megalodon, meaning "big tooth", it is regarded as one of the largest and most powerful predators to have ever lived.
While regarded as one of the largest and most powerful predators to have ever lived, megalodon is only known from fragmentary remains, and its appearance and maximum size are uncertain.
Like modern sharks, megalodon's skeleton was made mostly of cartilage. As a result, nothing remains of the creature except its teeth, which were made of a bone-like material.
That's enough, though, for scientists to get a sense of what megalodon looked like. "You can tell a lot based on just small parts of the bone," Shiffman explained. For example, "a lot of dinosaurs are known from a small part of bone."
Megalodon probably had a major impact on the structure of marine communities. The fossil record indicates that it had a cosmopolitan distribution. It probably targeted large prey, such as whales, seals and sea turtles. Juveniles inhabited warm coastal waters and fed on fish and small whales.
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Although we will mainly be discussing Megalodon today, Jack’s research goes way beyond the legendary giant. He studies the functional diversity of sharks through time, which essentially means understanding the ecological roles played by sharks across the last 66 million years.
Scientists have argued whether its body form was more stocky or elongated than the modern lamniform sharks. Maximum body length estimates between 14.2 and 24.3 metres (47 and 80 ft) based on various analyses have been proposed, though the modal lengths for individuals of all ontogenetic stages from juveniles to adults are estimated at 10.5 meters (34 ft).
As far as we know, megalodon was the largest shark to have ever existed. Using the size of their teeth, scientists estimate that megalodon could have reached a maximum length of twenty metres - but more conservative estimates place it at around fifteen metres long. It was a predator, feeding on large whales.
We know this from whale bone fossils that have megalodon teeth embedded in them! And, we know that megalodon roamed the seas from the Miocene to the Pliocene epochs, roughly 23 - 3.6 million years ago.
Another example of how intimidating megalodon could be: Where modern great whites hunt dolphins, scientists think megalodon hunted whales, or at least their ancestors, by biting off their tails and flippers.
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"Modern great whites will scavenge on a whale, but not actually take a [live] whale," Klimley said in an interview Tuesday.
Some studies suggest megalodon, which lived from about 16 million years ago until about 2 million years ago, had the most powerful bite of any creature that ever lived-strong enough to crush an automobile and far stronger than that of the great white shark or even Tyrannosaurus rex.
“There have been a couple of previous studies that have tried to calculate [megalodon’s bite force] - most of them will extrapolate from the great white Shark because their teeth, despite those distinct differences, are broadly similar in that they’re both big, triangular and serrated.” Jack explains.
Megalodon: The Greatest Predator That Ever Lived
“And the original paper calculated the great white sharks bite force and found it to be one of the highest of the animal kingdom today. Megalodon’s was at least an order of magnitude larger: the maximum bite force they got was 180 ,000 Newtons. Which if that’s accurate, that is the strongest bite force we know of of any living animal, living or extinct, in history.”
So, we know that megalodon was a huge shark, with a bite force to match.
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Physical Characteristics and Reconstruction
But what did they actually look like? Jack has been leading on research that modelled the size and proportions of megalodon, using just their teeth, some exceptionally well-preserved vertebrae, and some examples of modern-day sharks with similar lifestyles.
Megalodon is in the order Lamniformes, or the mackerel sharks (the same as white sharks). This means that there were 15 potential ‘analogues’ from the extant lamniforms that Jack could choose from - comparable species from present day.
Of these fifteen extant species, Jack chose those that had potentially similar diets and physiological traits to megalodon. Specifically, Jack was looking at regional endothermy (which we covered in detail on a recent episode with Haley Dolton!).
Essentially, regional endothermy is a trait exclusive to the lamniforms that allows them to heat certain parts of their body, and retain that heat. It is though that megalodon was regionally endothermic - which makes sense, given it’s lifestyle as an apex superpredator.
Regional endothermy would have allowed megalodon to swim faster and cover longer distances, much like today’s apex sharks. So, Jack selected five current species that had been shown to have similar lifestyles and physiological traits to megalodon: the porbeagle shark, short and long-fin mako sharks, salmon sharks and, of course, the great white shark.
Using measurements of the body proportions of these sharks compared against their total length, and with fossilised megalodon teeth, Jack and his team were able to ‘reconstruct’ megalodon. The result? Essentially a bulky, stocky lamnid, or in jack’s words, “an absolute unit of a shark”!
Jack and his team made three ‘versions’ of megalodon: a ‘baby’ megalodon, which still would have been an astonishing three metres long, a juvenile megalodon at eight metres, and an adult at sixteen metres long. For the latter, the size of the fins alone is mind-blowing.
According to the model, a sixteen metre adult would have had a dorsal fin the same size as an average human! They also had long, elongated pectoral fins, to provide that huge body with enough lift to propel itself through the water.
“It perhaps looked more like a salmon shark or porbeagle, with a stockier, shorter snout….or perhaps it looked more mako-like. But generally we think it looks essentially like a stocky lamnid.” In a very basic sense, a very big version of your ‘typical’ sharky shark!
Do you remember the exceptionally rare fossilised megalodon vertebrae we talked about earlier? Well, when it came to creating the most complete 3-D reconstruction of megalodon to date, these came in very handy.
Back in the 1860s, an entire vertebral column of megalodon was found. There were over 140 vertebrae in total, and from the texture, size and colouring, it could be deduced they were all from the same individual shark. The specimens essentially sat in a museum for 70 years, until a team led by Michael Godfrey arrived to reconstruct the largest shark that ever lived.
Later, Jack’s future PhD supervisor and director of the Pimiento Research Group Dr Catalina Pimiento, along with Professor John Hutchinson - an expert in 3D modelling of extinct taxa - managed to 3D scan the entire vertebral column.
But there were still some gaps that needed filling…the rest of the shark’s body, to be exact. And this is where Jack came in! Using a 3D body scan of a great white shark and some impressive modelling skills, they were able to fully reconstruct the megalodon’s body, which gave them critical insights into not only it’s size and body mass, but also the type of life it might have lived.
For starters, Jack’s work estimated that a 15.9 metre shark would have weighed an astonishing 60 tons! They also were able to figure out that megalodon could cruise around the ocean at speeds of about 1.4 metres per second - similar to a typical great white shark - which fit with the theory that megalodon was an active, agile predator.
And what is essential for that kind of lifestyle? A lot of calories! “We found a stomach capacity from about 10 ,000 litres, which was big enough to fit an entire killer whale.” Says Jack. “So that gave us, that gave us a nice sort of edge to think, okay, this thing’s trophic level is probably higher. They can eat a killer whale, which is of course famously the top predator in today’s oceans…and, a megalodon of our model size would have needed up to 98,000 kilocalories every day.”
Does that mean that megalodon would have needed to be constantly hunting to sustain itself? Well, not exactly.
“Interestingly, megalodon could have sustained itself by eating either a lot of small whales, or by eating one very big whale and then undertaking a transoceanic migration for two months.” Explains Jack. “And what we find exciting about that is that we know great white sharks undertake migrations that long. There’s the famous great white shark, Nicole, that went from Gansbaai in South Africa all the way to Australia and back again. So we like to think Megalodon was doing this too.
And incredibly excitingly, just last year, a paper was published that found essentially an in situ megalodon tooth in the middle of the Pacific Ocean. They did not find any evidence that had been moved a lot by geological activity. And in my mind, the only biological explanation for this is that a megalodon was taking a meal during a migration across the Pacific Ocean. It killed something and lost the tooth in that time. So it’s been very nice to see fossil evidence supporting that coming out.”
Although the megalodon dwarfed its living cousin-the great white-in size and weight, scientists say the great white actually looks pretty similar, with both possessing large teeth and a blunt snout.
"If you picture a megalodon as a 50-foot [16-meter] great white, you're well on your way to what this animal was probably like," Shiffman said.
A common misconception about megalodon is that they essentially looked like a giant version of the great white shark. Previously, scientists believed that white sharks were direct descendants of megalodon, but thanks to further discoveries the shark family tree has now changed.
It turns out there are very slight differences in their teeth. The teeth of megalodon are thicker, and have a dental band not present in that of a white shark’s. Both are serrated, like a steak knife - typical for an apex carnivore, suited for tearing and cutting meat - but under a microscope the serrations are subtly different between the species.
It may not sound like much, but it was enough evidence to suggest that, while megalodon would have had similar ecological traits to a white shark, they are in fact from different lineages.
It is now widely understood that megalodon was the last of the ‘megatooth’ sharks, a group of giant mackerel sharks that steadily got larger and larger. Further, the last common ancestor shared between them and white sharks was back in the Cretaceous period - some 145 to 66 million years ago.
From there, the ancestors of megalodon and white sharks went their separate ways and had completely different evolutionary trajectories. The megatooths themselves were very interesting.
They are known as a ‘chronospecies’, where there are only subtle changes through time. The earliest known species is Otodus obliquus, which was already around eight metres long - still bigger than the largest macro-predatory shark alive today, but not quite as big as the filter feeders.
Over time, the megatooths evolved to become larger, with bigger and more serrated teeth. This might be due to their diet. Around the same time, marine mammals began to evolve, also becoming bigger and faster.
There is still debate around this, but there are some fossils that show evidence of Otodus’ feeding habits. Some fossilied whale bones have bite marks that have been matched to megalodon teeth, or they have been found in the same location as the teeth themselves. There are also some pretty gruesome fossils that suggest a whale’s vertebrae was almost snapped in two by a potential megalodon bite!
Scientists have even been able to look at how the bone healed and regrew to estimate how long the whale might have lasted with such a nasty injury - potentially about six weeks.
“I suspect this poor whale was in agony for those last six weeks.” Says Jack. But the severity of the whale’s injury demonstrates how powerful a bite megalodon would have had.
Another factor in megalodon's decline may have been the rise of competitors such as killer whales. "Being social hunters, it has been suggested that they out-competed megalodon's hypothesized solitary hunting style," Catalina Pimiento, a shark researcher studying megalodon at the University of Florida, explained in a recent blog post.
Size comparison of a human, great white shark, and megalodon.
The Mystery of Megalodon's Extinction
For reasons that are still unclear, megalodon went extinct about 2 million years ago, during the middle Miocene era.
One hypothesis, said Klimley, is that megalodon was unable to adapt to changing ocean conditions.
Megalodon thrived during a time when the Earth's oceans were generally much warmer, and conditions were much more uniform.
But throughout the Miocene, the Isthmus of Panama started forming, culminating with the closure of the Central American Seaway around 3 million years ago.
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