A school lesson leads to more precise measurements of the extinct megalodon shark, one of the largest fish ever.
- A new method estimates the ancient megalodon shark was as long as 65 feet.
- The megalodon was one of the largest fish that ever lived.
- The new model uses the width of shark teeth to estimate its overall size.
A Florida student figured out a way to more accurately measure the size of one of the largest fish that ever lived – the extinct megalodon shark – and found that it was even larger than previously estimated.
The megalodon (officially named Otodus megalodon, which means "Big Tooth") lived between 3.6 and 23 million years ago and was thought to be about 34 feet long on average, reaching the maximum length of 60 feet. Now a new study puts that number at up to 65 feet (20 meters).
Homework assignment leads to a discovery
The study, published in Palaeontologia Electronica, used new equations extrapolated from the width of megalodon's teeth to make the improved estimates. The paper's lead author, Victor Perez, developed the revised methodology while he was a doctoral student at the Florida Museum of Natural History. He got the idea while teaching students, noticing a range of discrepancies in the results they were getting.
Students were supposed to calculate the size of megalodon based on the ancient fish's similarities to the modern great white shark. They utilized the commonly accepted method of linking the height of a shark's tooth to its total body length. As the press release from the Florida Museum of Natural History expounds, this method involves locating the anatomical position of a tooth in the shark's jaw, measuring the tooth "from the tip of the crown to the line where root and crown meet," and using that number in an appropriate equation.
But while carrying out calculations in this way, some of Perez's students thought the shark would have been just 40 feet long, while others were calculating 148 feet. Teeth located toward the back of the mouth were yielding the largest estimates.
"I was going around, checking, like, did you use the wrong equation? Did you forget to convert your units?" said Perez, currently the assistant curator of paleontology at the Calvert Marine Museum in Maryland. "But it very quickly became clear that it was not the students that had made the error. It was simply that the equations were not as accurate as we had predicted."
Found in North Carolina, these 46 fossils are the most complete set of megalodon teeth ever excavated.Credit: Jeff Gage/Florida Museum
The new approach
Perez's math exercise demonstrated that the equations in use since 2002 were generating different size estimates for the same shark based on which tooth was being measured. Because megalodon teeth are most often found as standalone fossils, Perez focused on a nearly complete set of teeth donated by a fossil collector to design a new approach.
Perez also had help from Teddy Badaut, an avocational paleontologist in France, who suggested using tooth width instead of height, which would be proportional to the length of its body. Another collaborator on the revised method was Ronny Maik Leder, then a postdoctoral researcher at the Florida Museum, who aided in the development of the new set of equations.
The research team analyzed the widths of fossil teeth that came from 11 individual sharks of five species, which included megalodon and modern great white sharks, and created a model that connects how wide a tooth was to the size of the jaw for each species.
"I was quite surprised that indeed no one had thought of this before," shared Leder, who is now director of the Natural History Museum in Leipzig, Germany. "The simple beauty of this method must have been too obvious to be seen. Our model was much more stable than previous approaches. This collaboration was a wonderful example of why working with amateur and hobby paleontologists is so important."
Why use teeth?
In general, almost nothing of the super-shark survived to this day, other than a few vertebrae and a large number of big teeth. The megalodon's skeleton was made of lightweight cartilage that decomposed after death. But teeth, with enamel that preserves very well, are "probably the most structurally stable thing in living organisms," Perez said. Considering that megalodons lost thousands of teeth during a lifetime, these are the best resources we have in trying to figure out information about these long-gone giants.
Researchers suggest megalodon's large jaws were very thick, made for grabbing prey and breaking its bones, exerting a bite force of up to 108,500 to 182,200 newtons.
Megalodon tooth compared to two great white shark teeth. Credit: Brocken Inaglory / Wikimedia.
Limitations of the new model
While the new model is better than previous methods, it's still far from perfect in precisely figuring out the sizes of animals which lived so long ago and left behind few if any full remains. Because individual sharks come in a variety of sizes, Perez warned that even their new estimates have an error range of about 10 feet when it comes to the largest animals.
Other ambiguities may affect the results, such as the width of the megalodon's jaw and the size of the gaps between its teeth, neither of which are accurately known. "There's still more that could be done, but that would probably require finding a complete skeleton at this point," Perez pointed out.
How did the megalodon go extinct?
Environmental changes that led to fluctuations in sea levels and disturbed ecosystems in the oceans likely led to the demise of these enormous ancient sharks. They were just too big to be sustained by diminishing food resources, says the ReefQuest Centre for Shark Research.
A 2018 study suggested that a supernova 2.6 million years ago hit Earth's atmosphere with so much cosmic energy that it resulted in climate change. The cosmic rays that included particles called muons might have caused a mass extinction of giant ocean animals ("the megafauna") that included the megalodon by causing mutations and cancer.
Scientists, led by Adrian Melott, professor emeritus of physics and astronomy at the University of Kansas, estimated that "the cancer rate would go up about 50 percent for something the size of a human — and the bigger you are, the worse it is. For an elephant or a whale, the radiation dose goes way up," as he explained in a press release.
A new study bases its calculations on more than the great white shark.
- Previous estimates of the megalodon's size were based solely on its teeth compared to the star of "Jaws."
- The prehistoric monster is as closely related to other sharks.
- Imagine just a dorsal fin as tall as you are.
For anyone already terrified by ferocious sharks — few of them actually are, of course — the prehistoric megalodon, Otodus megalodon, goes several steps beyond a nightmare. Not much is known about the animal that roamed the seas from 23 million to about three million years ago. The most definitive fossils are triangular teeth that are larger than a human hand, really not much from which to extrapolate a complete picture of the shark. Even so, they suggest a gargantuan predator. Have you seen "The Meg"?
Now a new, open-source study from the University of Bristol and Swansea University published in the journal Scientific Reports purports to have figured the megalodon's true dimensions, and they don't disappoint.
What’s different about this analysis
Previous estimates of the megalodon's size have been based on the great white shark, which can exceed 20 feet in length — that's about half the length of an average school bus. The idea has been, essentially, that since a great white's tooth is about 2 inches long — the biggest one ever found is 2.5 inches — and most megalodon teeth seem to be in the neighborhood of six inches — the largest one found is 7.4 inches — then the megalodon must have been about three times as big as a great white. The suggestion is that if great whites can bite with two tonnes of pressure (4400 pounds), then the megalodon's bite must have been significantly more powerful.
This may not be a completely fair comparison, however, according to one of the study's authors, Catalina Pimiento of Swansea. She tells University of Bristol that "Megalodon is not a direct ancestor of the Great White but is equally related to other macropredatory sharks such as the Makos, Salmon shark and Porbeagle shark, as well as the Great white." To arrive at their measurements the researchers, "pooled detailed measurements of all five to make predictions about Megalodon."
To try and work out the proportions of the prehistoric shark based on this larger group of contemporary sharks, the researchers investigated how their bodies change as they mature. "Before we could do anything," says co-author Mike Benton, "we had to test whether these five modern sharks changed proportions as they grew up. If, for example, they had been like humans, where babies have big heads and short legs, we would have had some difficulties in projecting the adult proportions for such a huge extinct shark."
It turned out, surprisingly, that though these sharks get larger as they grow up, their body proportions don't really change much. "This means we could simply take the growth curves of the five modern forms and project the overall shape as they get larger and larger — right up to a body length of 16 meters," adds lead author Jack Cooper.
Cooper has always been, as he puts it, "mad about sharks." He's worked and dived, in a steel cage, with great whites. He enthuses, "It's that sense of danger, but also that sharks are such beautiful and well-adapted animals that makes them so attractive to study."
The megalodon’s revised measurements
Credit: Reconstruction by Oliver E. Demuth/Scientific Reports
The study proposes the following approximate measurements for a full-grown megalodon:
- Length: about 16 meters (52.5 feet). A full-size school bus is just 45 feet long
- Head size: about 4.65 meters long (15.3 feet)
- Dorsal fin: about 1.62 meters tall (5.3 feet). A person could stand on the back of a megalodon and be about as tall as the fin.
- Tail fin: about 3.85 meters high (12.6 feet)
Let's just hope this sucker is really extinct.