Cannibalism in the womb may have helped make megalodon sharks giants

The largest sharks ever to hunt in Earth’s oceans may have gotten so big thanks to their predatory behavior in the womb, scientists report October 5 in Historical Biology.

The idea emerged from a study that first analyzed the sizes and shapes of modern and ancient shark teeth, using those data to estimate body sizes of the fish. Paleobiologist Kenshu Shimada of DePaul University in Chicago and colleagues focused on an order of sharks called lamniformes, of which only about 15 species still exist today, including fierce, fast great white and mako sharks as well as filter-feeding basking sharks (SN: 8/2/18).

Well over 200 lamniform species existed in the past, some of them quite large, Shimada says. But none is thought to have rivaled Otodus megalodon, commonly called megalodon, which lived between about 23 million and 2.5 million years ago. Determining just how giant these creatures were

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How Cannibalism in the Womb May Have Made Megalodon a Titanic Terror | Science

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

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