Oct. 5 (UPI) -- New analysis of body size among the different genera in the shark order Lamniformes suggests the megatooth shark megalodon was exceptionally massive.
Mature megalodon sharks, which swam the oceans between 15 million and 3.6 million years ago, reached lengths of 50 feet.
For as long as scientists have been finding and studying megalodon fossils, they've been aware of the shark's impressive size, but for the new study, published this week in the journal Historical Biology, researchers wanted to better understand how the species' size compared with maximum sizes of its many relatives.
Megalodon is a member of a group of sharks known as lamniforms. Most extinct lamniform species are known only by their fossilized teeth, but by analyzing the relationship between teeth and body size among present-day non-planktivorous lamniforms, researchers developed an equation for estimating the body sizes of extinct lamniform shark species.
When researchers estimated the maximum body sizes for past and present lamniform genera, they found the other non-planktivorous groups faced size limits of 23 feet. Only plankton-eating sharks, the whale shark and basking shark, came close to matching megalodon's size.
Megalodon, the research showed, was truly an outlier.
"This is compelling evidence for the truly exceptional size of megalodon," study co-author Michael Griffiths, a professor of environmental science at William Paterson University in New Jersey, said in a news release.
The new findings also showed that sharks during the Cenozoic Era, the period following the disappearance of the dinosaurs and continuing into modern times, have reacher much larger sizes than sharks living during the Mesozoic Era, when dinosaurs still roamed Earth.
Scientists have previously suggested warm-bloodedness best explains the lamniform gigantism found among several lineages, but the latest research suggests unique reproductive strategies might have played an equally important role. Researchers estimate that in some lamniform species, early hatched embryos grew to large sizes by cannibalizing the remaining eggs.
Because large species play an outsized role in shaping ecosystems, researchers argue that is important to more accurately characterize body size among ancient lineages.
"Lamniform sharks have represented major carnivores in oceans since the age of dinosaurs, so it is reasonable to assert that they must have played an important role in shaping the marine ecosystems we know today," said lead study author Kenshu Shimada, a paleobiologist at DePaul University in Chicago.
"This work represents a critical advancement in our understanding of the evolution of this ocean giant," said study co-author Martin Becker, professor of environmental science at William Paterson University.