A new study, published in the journal “Palaeontologia Electronica”, has revealed new evidence about the size, body shape, biology, and lifestyle of the Megalodon, the legendary giant shark that ruled the oceans between 15 and 3.6 million years ago. The research, coordinated by Professor Kenshu Shimada of DePaul University in Chicago, involved experts from nine countries and four continents, including the University of Pisa - the only Italian institution to participate in this study.
Scientists have analysed an extraordinary fossil: a partial vertebral column consisting of 141 vertebrae, approximately 11 metres long, found in Belgium more than a century ago. Research on body proportions in living and extinct sharks has revealed that the Belgian specimen was over 16 metres long, while the largest individuals of the species could have reached over 24 metres, with a maximum body mass of about 94 tonnes.
Schematic and hypothetical reconstruction of the body shape of a 24.3-meter-long Megalodon. Although the silhouette of a swimmer is shown next to the shark's schematic drawing to provide an idea of its size, it should be emphasized that the Megalodon is an extinct species that did not coexist with humans.
However, the most surprising discovery concerns the shape of the Megalodon’s body: contrary to previous reconstructions, which portrayed it as an oversized great white shark, the team has suggested a closer resemblance to the lemon shark (Negaprion brevirostris), which has a more slender body. Only an elongated shape would have made the Megalodon a fairly efficient swimmer despite its enormous size. Researchers have also observed that the largest modern sharks, such as the whale shark (Rhincodon typus) and the basking shark (Cetorhinus maximus), have relatively slender bodies, which makes them efficient swimmers despite their large size.
Alberto Collareta (on the left).
“Known under the scientific name Otodus megalodon (or Carcharocles megalodon), this famous protagonist of the oceans of the past is known above all for its large, triangular and serrated teeth, while the skeletal remains are extremely rare and fragmentary,” explains Professor Alberto Collareta, palaeontologist at the Department of Earth Sciences of the University of Pisa. The absence of complete Megalodon skeletons has often led researchers to reconstruct the appearance of this ancient sea giant as similar to that of the present-day great white shark (Carcharodon carcharias). This new research represents a fundamental step in understanding the biology of one of the largest predators in the history of our planet, challenging traditional reconstructions and presenting an even more fascinating image of the Megalodon”.
Another interesting aspect of the research concerns its reproduction. Researchers have estimated that the offspring of this species were already over three and a half metres long at birth. This suggests an ovoviviparous reproductive strategy, in which the more developed embryos feed on their unborn siblings, a phenomenon known as intrauterine cannibalism.
The study also hypothesises that the progressive disappearance of the Megalodon was at least partly linked to competition with the modern white shark, which appeared about 5 million years ago. Despite their different body shapes, these two formidable predators may have had similar food preferences: along with other environmental factors, competition with the great white shark for the same resources could have led to the extinction of the Megalodon.
The article “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” is freely accessible online at the following link: https://doi.org/10.26879/1502.
The authors are: Kenshu Shimada, Ryosuke Motani, Jake J. Wood, Phillip C. Sternes, Taketeru Tomita, Mohamad Bazzi, Alberto Collareta, Joel H. Gayford, Julia Türtscher, Patrick L. Jambura, Jürgen Kriwet, Romain Vullo, Douglas J. Long, Adam P. Summers, John G. Maisey, Charlie Underwood, David J. Ward, Harry M. Maisch IV, Victor J. Perez, Iris Feichtinger, Gavin J.P. Naylor, Joshua K. Moyer, Timothy E. Higham, João Paulo C.B. da Silva, Hugo Bornatowski, Gerardo Gonzalez-Barba, Michael L. Griffiths, Martin A. Becker and Mikael Siversson.