When you buy through links on our articles, Future and its syndication partners may earn a commission. The broad-shelled river turtle (Chelodina expansa) falls into a group known as side-neck turtles.

Forbes contributors publish independent expert analyses and insights. I write about biodiversity and the hidden quirks of the natural world. This one-ton turtle once ruled South America’s rivers — ...

It's a long-held idea that turtles can tuck their heads into their shells when threatened. But is it true? And is this protective trick why turtles the world over have shells today? The answer is that ...