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Revisiting body size trends and nursery areas of the Neogene megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), reveals Bergmann’s rule possibly enhanced its gigantism in cooler waters

2022; Taylor & Francis; Volume: 35; Issue: 2 Linguagem: Inglês

10.1080/08912963.2022.2032024

1029-2381

Kenshu Shimada, Harry M. Maisch, Víctor Juan Ventosa Pérez, Martin A. Becker, Michael L. Griffiths,

Fish Biology and Ecology Studies

The late Neogene megatooth shark, Otodus megalodon, is known mainly from its gigantic teeth and possibly reached 18–20 m in total length (TL). We re-examine the previously proposed body size trends and nursery areas of O. megalodon by confining the previously used samples to upper anterior teeth offering more reliable TL estimates, and by taking paleolatitudes and sea-surface temperatures into consideration. We demonstrate that individuals of O. megalodon are on average larger in cooler water than those in warmer water – a pattern attributable to Bergmann's rule showing a latitudinal body size gradient at least for the eastern Pacific late Miocene and the western Atlantic early Pliocene assemblages. While it is still possible that neonatal O. megalodon could have utilised nursery areas, the previously identified paleo-nursery areas based on body size may reflect temperature-dependent trends rather than the inferred reproductive strategy. Thus, the gigantism of O. megalodon in cooler waters was possibly further enhanced by its cooler environment. If so, the corollary of this study is that not all populations of O. megalodon likely grew to gigantic sizes equally, where the common notion that the species reached 18–20 m TL should be applied primarily to populations in cooler environments.