Study: Megalodon’s body shape was closer to a lemon shark

The 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 shark—measuring some 52 feet (16 meters) in length with a body mass of 67.86 tons—able to execute bursts of high speed to attack prey, much like the significantly smaller great white shark.