The dwarf Mediterranean megalodon does not exist: it turned out to be just a myth
Recent research into the biology of the extinct Otodus megalodon, the largest predatory shark that ever lived, had suggested that Mediterranean populations reached significantly smaller sizes than those from other parts of the planet, giving rise to the term “Mediterranean dwarfism”. However, a new study led by the Cavanilles Institute of Biodiversity and Evolutionary Biology of the University of Valencia, in collaboration with several Spanish and Portuguese institutions, provides robust evidence that refutes this interpretation and demonstrates that Mediterranean specimens were not smaller than those from other regions.
29 de january de 2026
The study, which sheds new light on the biology and lifestyle of Otodus megalodon, focuses on analysing the fossil record from the Iberian Peninsula and dismantles the idea that Mediterranean individuals were generally smaller.
Otodus megalodon lived between the Miocene and the Pliocene and reached lengths of more than 15 metres. However, much of what is known about this species has traditionally been based on fossils from the Americas. This partial perspective led to hypotheses such as the so-called “Mediterranean dwarfism”, according to which megalodons from this basin would have had a smaller body size due to particular environmental conditions.
To test this idea, the research team, led by the University of Valencia, collected and analysed 335 fossil teeth from museums and scientific collections in Spain and Portugal, constituting the largest dataset assembled to date outside the American continent. Based on tooth size, the scientists estimated body length and compared Atlantic and Mediterranean populations.
The results show that Atlantic and Mediterranean megalodon specimens were very similar in size, ruling out the existence of widespread Mediterranean dwarfism. However, specimens from a specific Middle Miocene site – the Reverté quarries in north-eastern Spain – are clearly smaller.
According to the researchers, this difference is not due to broad climatic or geographical conditions, but rather to the fact that Reverté functioned as a genuine “nursery” or breeding ground. As occurs today in many shark species, juvenile individuals were concentrated in these environments, finding both food and protection from large predators.
The study therefore reinforces the idea that the use of nursery areas was a key strategy in the life history and evolutionary success of Otodus megalodon. Moreover, by filling an important geographical gap, the Iberian fossil record makes it possible to test alternative hypotheses and to gain a better understanding of how populations of one of the most iconic predators in the history of the oceans were structured.
The research was partially funded by public projects within the Spanish national R&D&I system and highlights the importance of palaeontological collections and international collaboration for reconstructing the history of life on Earth. Specifically, funding was provided by grant PID2023-147440OB-C21 from MICIU/AEI/10.13039/501100011033 and by research project PID2020-117373GA-I00 from the Spanish Ministry of Science and Innovation.
Article reference: Herraiz, J.L., Ferró,H.G, Botella, H., Reolid, M. & Martínez-Pérez, C. (2026) “The Iberian fossil record of †Otodus megalodon rejects Mediterranean dwarfism and supports nursery use”, Biol Lett (2026) 22 (1): 20250640.https://doi.org/10.1098/rsbl.2025.0640