Body-size trends of the extinct giant sharkCarcharocles megalodon: a deep-time perspective on marine apex predators

Abstract

AbstractThe extinct sharkCarcharocles megalodonis one of the largest marine apex predators ever to exist. Nonetheless, little is known about its body-size variations through time and space. Here, we studied the body-size trends ofC. megalodonthrough its temporal and geographic range to better understand its ecology and evolution. Given that this species was the last of the megatooth lineage, a group of species that shows a purported size increase through time, we hypothesized thatC. megalodonalso displayed this trend, increasing in size over time and reaching its largest size prior to extinction. We found thatC. megalodonbody-size distribution was left-skewed (suggesting a long-term selective pressure favoring larger individuals), and presented significant geographic variation (possibly as a result of the heterogeneous ecological constraints of this cosmopolitan species) over geologic time. Finally, we found that stasis was the general mode of size evolution ofC. megalodon(i.e., no net changes over time), contrasting with the trends of the megatooth lineage and our hypothesis. Given thatC. megalodonis a relatively long-lived species with a widely distributed fossil record, we further used this study system to provide a deep-time perspective to the understanding of the body-size trends of marine apex predators. For instance, our results suggest that (1) a selective pressure in predatory sharks for consuming a broader range of prey may favor larger individuals and produce left-skewed distributions on a geologic time scale; (2) body-size variations in cosmopolitan apex marine predators may depend on their interactions with geographically discrete communities; and (3) the inherent characteristics of shark species can produce stable sizes over geologic time, regardless of the size trends of their lineages.