Lesson gone wrong leads to new estimate of megalodon size – Florida Museum Science

A A more reliable way to estimate the size of the megalodon shows that the extinct shark may have been larger than previously thought, measuring up to 65 feet, nearly the length of two school buses. Previous studies had penned the massive predator at around 50 to 60 feet long.

The revised estimate is the result of new equations based on the width of the teeth of the megalodon – and started with a high school lesson gone awry.

Victor Perez, then a doctoral student at the Florida Museum of Natural History, guided students through a math exercise that used 3D printed replicas of fossil teeth from a real megalodon and a set of commonly used height-based equations. teeth to estimate the size of the shark. Cut. But something was wrong: Student calculations ranged from around 40 to 148 feet for the same shark. Perez went into troubleshooting mode.

“I was going around, checking, like, did you use the wrong equation?” Did you forget to convert your units? Said Perez, lead author of the study and now associate curator of paleontology at the Calvert Marine Museum in Maryland. “But it quickly became clear that it wasn’t the students who made the mistake. It was just that the equations weren’t as precise as we had expected.

Although the equations have been used extensively by scientists since their publication in 2002, the classroom exercise found that they generate varying size estimates for a single shark, depending on the tooth being measured.

“I was really surprised,” Perez said. “I think a lot of people saw this study and blindly accepted the equations.”

For more than a century, scientists have been trying to calculate the size of the megalodon, whose name means “big tooth”. But the only known remains of the dreaded shark that ruled the oceans around 23 to 3.6 million years ago are fossilized teeth and a few rare vertebrae. Like other sharks, the rest of the megalodon’s skeleton, including its jaw, was made up of light cartilage that quickly decomposed after death. Tooth enamel, however, “keeps very well,” Perez said. “It is probably the most structurally stable thing in living organisms.” Megalodon sharks lose thousands of teeth during their lifetime, leaving abundant traces of the species in the fossil record.

The most accepted methods for estimating megalodon length have used great white sharks as a modern indicator, relying on the relationship between tooth size and total body length. While great white sharks and megalodon belong to different families, they share similar predatory lifestyles and wide, triangular, jagged teeth like steak knives – ideal adaptations for hunting large, fleshy marine mammals such as whales. and dolphins, Perez said.

But these methods also present a challenge: to generate estimates of body length, they require the researcher to correctly identify the anterior position of a fossil tooth in a megalodon jawbone. As in humans, shark teeth vary in size and shape depending on where they are in the mouth, and megalodon teeth are most commonly found as free-standing fossils.

museum megalodon tooth specimen
Megalodon teeth can be up to 7 inches long and were specialized for feeding on large, fleshy prey, such as whales and dolphins.

Florida Museum Photo by Kristen Grace

So Perez was elated when fossil collector Gordon Hubbell donated an almost complete dentition of the same megalodon shark to the Florida Museum in 2015, reducing guesswork. After museum researchers scanned the teeth and made them available online, Perez collaborated with teacher Megan Higbee Hendrickson on a plan to incorporate them into her college program at the Academy of the Holy Names School in Tampa.

“We decided to have the kids 3D print the teeth, determine the size of the shark, and build a replica of its jawbone for our art show,” said Hendrickson.

Perez and Hendrickson co-designed a lesson for students based on the most popular method at the time to estimate the size of sharks: match the tooth to its position in the shark jaw, find the corresponding equation, measure tooth from the tip of the crown to the line where the root and crown meet and plug the number into the equation.

After a successful pilot test of a few teeth with the Hendrickson students, he expanded the lesson plan to include the megalodon teeth set for high school students at Delta Charter High School in Aptos, California. Perez had expected a slight variability of a few millimeters in their results, but this time the variations in student estimates reached over 100 feet. The further the position of a tooth was from the front of the jaw, the larger the size estimate.

After Perez detailed the results of the lesson in a fossil community newsletter, he received an email from Teddy Badaut, an amateur paleontologist in France. Badaut suggested a different approach. Why not measure the width of the teeth instead of the height? Previous research had suggested that the width of teeth was limited by the size of a shark’s jaw, which would be proportional to the length of its body.

Ronny Maik Leder, then a postdoctoral researcher at the Florida Museum, worked with Perez to develop a new set of equations based on tooth width.

By measuring the Hubbell tooth set, “we could actually summarize the width of the teeth and get a better approximation of the width of the jaw,” Perez said.

artist rendering of megalodon
When the megalodon was first described as a species, scientists believed it was the direct ancestor of the great white shark. Although the two species have similar teeth and eating habits, they last shared a common ancestor around 60 million years ago, Perez said.

Image courtesy of Tim Scheirer / Calvert Marine Museum

The researchers analyzed sets of fossil teeth from 11 individual sharks, representing five species, including the megalodon, its close relatives, and modern great white sharks.

By measuring the combined width of each tooth in a row, they developed a model of the width of an individual tooth relative to the jawbone for a given species. Now, when a paleontologist discovers a single megalodon tooth the size of his hand, he can compare its width to the average obtained in the study and get an accurate estimate of the size of the shark.

“I was quite surprised that indeed no one had thought of it before,” said Leder, now director of the Leipzig Natural History Museum, Germany. “The simple beauty of this method had to be too obvious to be seen. Our model was much more stable than previous approaches. This collaboration was a wonderful example of the importance of working with amateur and amateur paleontologists. “

Perez warned that because individual sharks vary in size, the team’s methods always have a margin of error of around 10 feet when applied to larger individuals. It’s also not clear exactly how wide and difficult the megalodon’s jawbone was to guess based solely on the teeth – some species of sharks have spaces between each tooth while the teeth of other species overlap.

“While this can potentially advance our understanding, we haven’t really addressed the issue of the size of the megalodon. There is still more to do, but that would probably require finding a complete skeleton at this point, ”he said.

megalodon teeth set
Unearthed from North Carolina, these 46 fossils constitute the most complete set of megalodon teeth ever found. Students 3D printed replicas of the teeth and used them to estimate the length of the megalodon.

Florida Museum Photo by Jeff Gage

Perez continues to teach the lesson of the megalodon tooth, but his focus has changed.

“Since then, we’ve used the lesson to talk about the nature of science – the fact that we don’t know everything. There are still unanswered questions, ”he said.

For Hendrickson, the lesson sparked his students’ enthusiasm for science in a way that textbooks couldn’t.

“Victor was an incredible role model for children. He is the personification of a young scientist who followed his childhood interest and made a career out of it. So many of these kids had never worked with or spoken to a scientist who respected their point of view and was ready to answer their questions.

The research was published in the open access journal Palaeontologia Electronica.

Leder and Badaut co-authored the study.

The research was based on work supported by the Florida Education Fund McKnight Doctoral Fellowship, the National Science Foundation Graduate Research Fellowship Program, and the NSF Advancing Informal STEM Learning Program.

Sources: Victor Perez, [email protected];
Megan Higbee Hendrickson, [email protected];
Ronny Leder, [email protected]

Screenwriters: Natalie van Hoose, [email protected], 352-273-1922;
Jerald Pinson, [email protected], 352-294-0452

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