Kenshu Shimada (1,2,3), Matthew F. Bonnan (4), Martin A. Becker (5), Michael L. Griffiths (5)
Historical Biology, January 2021. DOI: 10.1080/08912963.2020.1861608

Keywords

Elasmobranchii, Lamniformes, longevity, ontogeny, Otodontidae, reproduction

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.

How Our Software Was Used

Dragonfly was used for the segmentation of CT images.

Author Affiliation

(1) Department of Environmental Science and Studies, DePaul University, Chicago, IL, USA.
(2) Department of Biological Sciences, DePaul University, Chicago, IL, USA.
(3) Sternberg Museum of Natural History, Fort Hays State University, Hays, KS, USA.
(4) Biology Program, Stockton University, Galloway, NJ, USA.
(5) Department of Environmental Science, William Paterson University of New Jersey, Wayne, NJ, USA.