A groundbreaking study led by Professor Kenshu Shimada of DePaul University has provided new insights into the biology of the prehistoric giant shark Megalodon (Otodus megalodon), which once roamed the oceans globally from about 15 million to 3.6 million years ago. The study, conducted in collaboration with 28 experts in shark biology, paleontology, and vertebrate anatomy, sheds light on the shark’s body structure, size, and potential evolutionary relationships. These findings, published in the Palaeontologia Electronica journal, mark a significant advancement in our understanding of one of the most formidable marine predators ever to live.
Megalodon is mainly known through its teeth, vertebrae, and some scale fossils, as no complete skeletons have been discovered. Traditionally, the gigantic shark has been envisioned as a larger version of the modern great white shark (Carcharodon carcharias), largely because the two species share similar serrated teeth. This assumption has been reinforced by popular culture, especially in novels and films like The Meg, where the prehistoric shark is depicted as a massive version of its modern counterpart. However, the latest research challenges this notion by suggesting that Megalodon‘s body form likely differed from that of the great white shark in key ways.
A major contribution of the new study stems from the analysis of a nearly complete fossilized vertebral column of Megalodon discovered in Belgium. The fossil, which measures approximately 11 meters (36 feet) in length, represents the trunk portion of the shark’s body and provides valuable clues about its overall proportions. However, critical parts of the shark’s anatomy, including the head and tail, were missing from this specimen. The study sought to address this gap by estimating the lengths of these missing body parts.
The researchers conducted a comparative study involving 145 modern and 20 extinct species of sharks to examine the typical body proportions of sharks. By measuring the relative sizes of the head, trunk, and tail in these species, they were able to estimate the missing dimensions of Megalodon‘s body. Based on these comparisons, the team concluded that the head would have accounted for about 16.6% of the shark’s total length, while the tail would have made up roughly 32.6%. Applying these proportions to the 11-meter trunk fossil, the team estimated that the head of this Megalodon individual was approximately 1.8 meters (6 feet) long, and the tail was around 3.6 meters (12 feet) long. This brought the total length of the shark to an estimated 16.4 meters (54 feet).
The researchers also examined the size of Megalodon’s vertebrae to help refine their estimates of the shark’s size. The largest vertebra from the Belgian specimen measured 15.5 centimeters (6 inches) in diameter, but similar fossils from Denmark have been reported with vertebrae as large as 23 centimeters (9 inches) in diameter. If these larger vertebrae belong to the largest individual Megalodon, the researchers suggested that it could have reached a maximum length of approximately 24.3 meters (80 feet). This represents the largest scientifically supported estimate of the shark’s size, based on the available fossil evidence.
Professor Shimada, who led the study, emphasized that the size estimate of 24.3 meters is the largest plausible figure based on current data. However, he noted that further discoveries, such as more complete fossils, could either support or refine this estimate. The study’s findings are significant not only because they provide new insights into the size of Megalodon, but also because they challenge the longstanding assumption that it resembled a giant version of the modern great white shark.
In addition to examining Megalodon‘s size, the research team also explored the shark’s body shape. They compared the body proportions of Megalodon with those of modern-day sharks, including the great white, whale shark (Rhincodon typus), and basking shark (Cetorhinus maximus). These modern giants have more slender bodies compared to the stocky build of the great white shark. The researchers proposed that Megalodon may have had a similar body shape to the modern lemon shark (Negaprion brevirostris), which has a more slender, streamlined body that is better suited for fast swimming. This contrasts with the bulkier body of the great white shark, which, despite being capable of growing large, has physical limitations that prevent it from attaining truly gigantic sizes. The team’s findings suggest that Megalodon‘s more hydrodynamic body design may have contributed to its ability to grow to enormous sizes, as larger, stockier bodies are less efficient for swimming.
The study also sheds light on Megalodon‘s biological and behavioral traits. Based on the morphology of its teeth and scales, the researchers estimated that a fully grown Megalodon would have weighed approximately 94 tons if it reached the size of 24.3 meters (80 feet). The team also studied the fossilized scales from Megalodon and estimated that it likely cruised at a speed of 2.1 to 3.5 kilometers per hour (1.3 to 2.2 miles per hour), which is comparable to the cruising speed of the modern great white shark. Despite its massive size, Megalodon‘s speed would have been limited by its hydrodynamic constraints, which are shared by other large sharks.
The research also examined Megalodon‘s reproductive biology, based on the growth patterns found in its vertebral specimens. The team suggested that Megalodon likely gave birth to live young, with newborns measuring around 3.6 to 3.9 meters (12 to 13 feet) long. The growth patterns also indicated that the embryos may have engaged in a behavior known as “oophagy,” or egg-eating, where the developing embryos nourish themselves by consuming other eggs within the mother’s body.
Another important aspect of the study focused on the evolutionary relationship between Megalodon and the great white shark. The researchers suggested that the rise of the great white shark, which appeared around 5 million years ago, may have played a role in the eventual extinction of Megalodon. The two species likely competed for similar food sources, and the advent of the more efficient and faster great white may have outcompeted Megalodon, contributing to its gradual demise.
The study also provides new insights into the general biology of Megalodon and offers a valuable reference point for future studies. Although many of the researchers’ conclusions are tentative, they are based on data-driven analyses and provide a scientific framework for understanding the biology of one of history’s largest predators. Professor Shimada expressed hope that future discoveries of more complete fossil specimens could allow for further refinement of these interpretations.
More information: Reassessment of the possible size, form, weight, cruising speed, and growth parameters of the extinct megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), and new evolutionary insights into its gigantism, life history strategies, ecology, and extinction, Palaeontologia Electronica (2025). DOI: 10.26879/1502