There’s never been a bigger carnivorous shark than Otodus megalodon. At a maximum body size of 50 feet long, this ancient mako relative was the largest shark ever to chomp its way through the seas. No other shark species, even among its close relatives, grew quite so large. But how did megalodon become so exceptional?
A new study, published today in Historical Biology by DePaul University paleontologist Kenshu Shimada and colleagues, suggests that cannibalism in utero may have helped set up the rise of the largest meat-eating shark of all time. The researchers suggest that a biological connection existed between having large, hungry babies, a metabolism that ran warm and increases in size—with the appetites of baby sharks driving their mothers to eat more and get bigger, which led the babies to get bigger themselves.
Shimada and colleagues focused on the size of existing lamniform sharks, using measurements of today’s makos and their relatives to estimate the size of prehistoric sharks. By figuring out how body size relates to tooth size, the researchers were able to look at the fossil teeth of various extinct sharks and come up with refined estimates of how big those prehistoric fish were.
Most of the sharks were comparable in size to lamniformes alive today. Only four lineages of ancient lamniform shark got to be more than 20 feet in length, with Otodus megalodon being an extreme outlier at more than twice that maximum length. “We expected megalodon to be gigantic,” Shimada says, “but what surprised us was actually seeing in our data a 23-foot-gap between the size of megalodon and the size of the next largest carnivorous lamniform sharks.”
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