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. (1st February 2023)

• Record Type: Journal Article
• Authors: Shimada, Kenshu; Maisch, Harry M.; Perez, Victor J.; Becker, Martin A.; Griffiths, Michael L.
• Is Part Of: Historical biology. Volume 35:Number 2(2023)
• Page Start: 208
• Page End: 217
• Publication Date: 2023-02-01
• Subjects: Climate -- fossil record -- latitude -- oceanography -- population -- shark tooth; Paleobiology -- Periodicals; Biology -- Periodicals; Evolution -- Periodicals; Paleontology -- Periodicals; Biology -- Periodicals; Paleontology -- Periodicals; Evolution -- Periodicals; 560.5
• DOI: 10.1080/08912963.2022.2032024
• Languages: English
• ISSNs: 0891-2963

Abstract

ABSTRACT: 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.