Endothermic physiology of extinct megatooth sharks

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 120; no. 27
• Main Authors: Griffiths, Michael L., Eagle, Robert A., Kim, Sora L., Flores, Randon J., Becker, Martin A., Maisch, Harry M., Trayler, Robin B., Chan, Rachel L., McCormack, Jeremy, Akhtar, Alliya A., Tripati, Aradhna K., Shimada, Kenshu
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 26.06.2023
• Subjects: Science & Technology - Other Topics
• ISSN: 0027-8424

The evolution of the extinct megatooth shark,Otodus megalodon, and its close phylogenetic relatives remains enigmatic. A central question persists regarding the thermophysiological origins of these large predatory sharks through geologic time, including whetherO. megalodonwas ectothermic or endothermic (including regional endothermy), and whether its thermophysiology could help to explain the iconic shark’s gigantism and eventual demise during the Pliocene. To address these uncertainties, we present unique geochemical evidence for thermoregulation inO. megalodonfrom both clumped isotope paleothermometry and phosphate oxygen isotopes. Our results show thatO. megalodonhad an overall warmer body temperature compared with its ambient environment and other coexisting shark species, providing quantitative and experimental support for recent biophysical modeling studies that suggest endothermy was one of the key drivers for gigantism inO. megalodonand other lamniform sharks. The gigantic body size with high metabolic costs of having high body temperatures may have contributed to the vulnerability ofOtodusspecies to extinction when compared to other sympatric sharks that survived the Pliocene epoch.