New fossil tells how piranhas got their teeth. National Evolutionary Synthesis Center, June 25, 2009. How did piranhas — the legendary freshwater fish with the razor bite — get their telltale teeth? An international team of researchers uncover a jawbone that sheds some light on the bite. Picked up by Science Magazine, National Geographic News, Fox News, US News and World Report, MSNBC, and the Philadelphia Inquirer.