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the mighty, mighty megalodon Study: Megalodons body shape was closer to a lemon shark Also: Baby megalodons were likely the size of great white sharks and capable of hunting marine mammals Jennifer Ouellette Mar 9, 2025 7:01 pm | 10 Megalodon jaws at the Tellus Science Museum near Cartersville, Georgia Credit: JJonahJackalope/CC BY-SA 4.0 Megalodon jaws at the Tellus Science Museum near Cartersville, Georgia Credit: JJonahJackalope/CC BY-SA 4.0 Story textSizeSmallStandardLargeWidth *StandardWideLinksStandardOrange* Subscribers only Learn moreThe giant extinct shark species known as the megalodon has captured the interest of scientists and the general public alike, even inspiring the 2018 blockbuster film The Meg. The species lived some 3.6 million years ago and no complete skeleton has yet been found. So there has been considerable debate among paleobiologists about megalodon's size, body shape and swimming speed, among other characteristics.While some researchers have compared megalodon to a gigantic version of the stocky great white shark, others believe the species had a more slender body shape. A new paper published in the journal Palaeontologia Electronica bolsters the latter viewpoint, also drawing conclusions about the megalodon's body mass, swimming speed (based on hydrodynamic principles), and growth patterns.As previously reported, the largest shark alive today, reaching up to 20 meters long, is the whale shark, a sedate filter feeder. As recently as 4 million years ago, however, sharks of that scale likely included the fast-moving predator megalodon (formally Otodus megalodon). Due to incomplete fossil data, we're not entirely sure how large megalodons were and can only make inferences based on some of their living relatives.Thanks to research published in 2023 on its fossilized teeth, we're now fairly confident that megalodon shared something else with these relatives: it wasn't entirely cold-blooded and kept its body temperature above that of the surrounding ocean. Most sharks, like most fish, are ectothermic, meaning that their body temperatures match those of the surrounding water. But a handful of species, part of a group termed mackerel sharks, are endothermic: They have a specialized pattern of blood circulation that helps retain some of the heat their muscles produce. This enables them to keep some body parts at a higher temperature than their surroundings.Of particular relevance to this latest paper is a 2022 study by Jack Cooper of Swansea University in the UK and his co-authors. In 2020, the team reconstructed a 2D model of the megalodon, basing the dimensions on similar existing shark species. The researchers followed up in 2022 with a reconstructed 3D model, extrapolating the dimensions from a megalodon specimen (a vertebral column) in Belgium. Cooper concluded that a megalodon would have been a stocky, powerful sharkmeasuring some 52 feet (16 meters) in length with a body mass of 67.86 tonsable to execute bursts of high speed to attack prey, much like the significantly smaller great white shark. (H) One of the largest vertebrae of Otodus megalodon; (I and J) CT scans showing cross-sectional views. Credit: Shimada et al., 2025 Not everyone agreed, however, Last year, a team of 26 shark experts led by Kesnshu Shimada, a paleobiologist at DePaul University, further challenged the great white shark comparison, arguing that the super-sized creature's body was more slender and possibly even longer than researchers previously thought. The team concluded that based on the spinal column, the combination of a great white build with the megalodon's much longer length would have simply proved too cumbersome.A fresh approachNow Shimada is back with a fresh analysis, employing a new method that he says provides independent lines of evidence for the megalodon's slender build. "Our new study does not use the modern great white shark as a model, but rather simply asks, 'How long were the head and tail based on the trunk [length] represented by the fossil vertebral column?' using the general body plan seen collectively in living and fossil sharks," Shimada told Ars.Shimada and his co-authors measured the proportions of 145 modern and 20 extinct species of shark, particularly the head, trunk, and tail relative to total body length. Megalodon was represented by a Belgian vertebral specimen. The largest vertebra in that specimen measured 15.5 centimeters (6 inches) in diameter, although there are other megalodon vertebrae in Denmark, for example, with diameters as much as 23 centimeters (9 inches).Based on their analysis, Shimada et al, concluded that, because the trunk section of the Belgian specimen measured 11 meters, the head and tail were probably about 1.8 meters (6 feet) and 3.6 meters (12 feet) long, respectively, with a total body length of 16.4 meters (54 feet) for this particularly specimen. That means the Danish megalodon specimens could have been as long as 24.3 meters (80 feet). As for body shape, taking the new length estimates into account, the lemon shark appears to be closest modern analogue. "However, the exact position and shape of practically all the fins remain uncertain," Shimada cautioned. "We are only talking about the main part of the body." Credit: DePaul University/Kenshu Shimada The team also found that a 24.3-meter-long megalodon would have weighed a good 94 tons with an estimated swimming speed of 2.1-3.5 KPM (1.3-2.2 MPH). They also studied growth patterns evident in the Belgian vertebrae, concluding that the megalodon would give live birth and that the newborns would be between 3.6 to 3.9 meters (12-13 feet) longi.e., roughly the size of a great white shark. The authors see this as a refutation of the hypothesis that megalodons relied on nursery areas to rear their young, since a baby megalodon would be quite capable of hunting and killing marine mammals based on size alone.In addition, "We unexpectedly unlocked the mystery of why certain aquatic vertebrates can attain gigantic sizes while others cannot," Shimada said. "Living gigantic sharks, such as the whale shark and basking shark, as well as many other gigantic aquatic vertebrates like whales have slender bodies because large stocky bodies are hydrodynamically inefficient for swimming."That's in sharp contrast to the great white shark, whose stocky body becomes even stockier as it grows. "It can be 'large' but cannot [get] past 7 meters (23 feet) to be 'gigantic' because of hydrodynamic constraints," said Shimada. "We also demonstrate that the modern great white shark with a stocky body hypothetically blown up to the size of megalodon would not allow it to be an efficient swimmer due to the hydrodynamic constraints, further supporting the idea that it is more likely than not that megalodon must have had a much slenderer body than the modern great white shark."Shimada emphasized that their interpretations remain tentative but they are based on hard data and make for useful reference points for future research.An "exciting working hypothesis"For his part, Cooper found a lot to like in Shimada et al.'s latest analysis. "I'd say everything presented here is interesting and presents an exciting working hypothesis but that these should also be taken with a grain of salt until they can either be empirically tested, or a complete skeleton of megalodon is found to confirm one way or the other," Cooper told Ars. "Generally, I appreciate the paper's approach to its body size calculation in that it uses a lot of different shark species and doesn't make any assumptions as to which species are the best analogues to megalodon." Shark biologists now say a lemon shark, like this one, is a better model of the extinct megalodon's body than the great white shark. Credit: Albert Kok Cooper acknowledged that it makes sense that a megalodon would be slightly slower than a great white given its sheer size, "though it does indicate we've got a shark capable of surprisingly fast speeds for its size," he said. As for Shimada's new growth model, he pronounced it "really solid" and concurred with the findings on birthing with one caveat. "I think the refutation of nursery sites is a bit of a leap, though I understand the temptation given the remarkably large size of the baby sharks," he said. "We have geological evidence of multiple nurseriesnot just small teeth, but also geological evidence of the right environmental conditions."He particularly liked Shinada et al.'s final paragraph. "[They] call out 'popular questions' along the lines of, 'Was megalodon stronger than Livyatan?'" said Cooper. "I agree with the authors that these sorts of questionsones we all often get asked by 'fans' on social mediaare really not productive, as these unscientific questions disregard the rather amazing biology we've learned about this iconic, real species that existed, and reduce it to what I can only describe as a video game character."Regardless of how this friendly ongoing debate plays out, our collective fascination with megalodon is likely to persist. "It's the imagining of such a magnificently enormous shark swimming around our oceans munching on whales, and considering that geologically speaking this happened in the very recent past," said Cooper of the creature's appeal. "It really captures what evolution can achieve, and even the huge size of their teeth alone really put it into perspective."DOI: Palaeontologia Electronica, 2025. 10.26879/1502 (About DOIs).Jennifer OuelletteSenior WriterJennifer OuelletteSenior Writer Jennifer is a senior writer at Ars Technica with a particular focus on where science meets culture, covering everything from physics and related interdisciplinary topics to her favorite films and TV series. Jennifer lives in Baltimore with her spouse, physicist Sean M. Carroll, and their two cats, Ariel and Caliban. 10 Comments
