Ontogenetic growth pattern of the extinct megatooth shark Otodus megalodon—implications for its reproductive biology, development, and life expectancy

ABSTRACT

The extinct megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), is known primarily from its gigantic teeth in the late Neogene marine fossil record. It is known to reach at least 14.1‒15.3 m in length, but its reproductive biology and ontogenetic growth pattern have remained largely in the realm of speculation. Here, we examined incremental growth bands in fossil vertebrae of a 9.2-m-long individual O. megalodon, revealing that the shark was born large, 2 m in length, and died at age 46. This large size at birth is characteristic of lamniform sharks and is indicative of live-bearing reproduction along with embryos’ intrauterine cannibalism behaviour in the form of oophagy. The trajectory of the generated growth curve beyond the age of death and the maximum length (about 15 m) calibrated from the largest known teeth of O. megalodon suggest that the species had a lifespan of at least 88–100 years with an average growth rate of about 16 cm/yr at least for the first 46 years. As one of the largest carnivores that ever existed on Earth, deciphering such growth parameters of O. megalodon is critical to understand the role large carnivores play in the context of the evolution of marine ecosystems.

KEYWORDS:

• Elasmobranchii
• Lamniformes
• longevity
• ontogeny
• Otodontidae
• reproduction

Acknowledgments

We sincerely thank the following IRSNB staff for supplying us archival photographs and micro-CT data (as part of the DIGIT03 project) of IRSNB P 9893: A. Folie, S. Beaudart, C. Cousin, J. Lalanne, and U. Lefèvre. We also thank W. Simpson (FMNH), N. Kohno, and C. Sakata (NSM) for access to the two tooth specimens illustrated in Figure 2, and H. Maisch (William Paterson University), E. Kast, and A. Akhtar (Princeton University) for their discussion with us on sharks. We appreciate comments and suggestions made by R. Boessenecker, P. Jambrua, and two anonymous reviewers that significantly improved the quality of this paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported in part by a National Science Foundation Sedimentary Geology and Paleobiology Award to Kenshu Shimada (Award Number 1830858) as well as to Michael Griffiths and Martin Becker (Award Number 1830581).