Otodus megalodon was a gigantic megatooth shark that lived in the world’s oceans from 23 to 3.6 million years ago. It could grow to the enormous size of at least 15 m long, making it one of the largest apex marine predators since the Mesozoic. In new research, paleontologists tested hypotheses relating to Otodus megalodon’s extinction by providing quantitative estimates of its body temperature. They found that thereby constraining its thermal physiology had body temperatures significantly elevated compared to other sharks, consistent with it having a degree of internal heat production as modern warm-blooded animals do.
Sharks are a group of cartilaginous fishes with a nearly 200-million-year geologic history.
The fossil record shows that numerous shark species appeared and disappeared through geologic time where many groups even survived through the end-Cretaceous mass extinction.
Today, there are over 500 species of sharks found in nearly every marine habitat, including the coastal epipelagic zone to below 1,000 m of depth in the abyssopelagic zone.
They play crucial roles in marine ecosystems as meso- and apex predators as well as potential food sources for older individuals or larger species.
The ability to regulate body temperature is evolutionarily profound because it is thought to have also acted as a key driver for the evolution of gigantism in predatory sharks.
In fact, Otodus megalodon — primarily known only from its gigantic teeth in the Late Neogene fossil record — is inferred to have been warm-blooded, or more precisely regionally endothermic, based on multiple lines of evidence.
“However, those findings were based on pure inference,” said William Paterson University’s Professor Michael Griffiths and colleagues.
“Our study provides the first empirical evidence of warm-bloodedness in the extinct shark.”
The researchers used a novel geochemical technique, involving clumped isotope thermometry and phosphate oxygen isotope…
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