When fish first started biting

Before fish began to invade land, about 365 million years ago, they had some big problems to solve. They needed to come up with new ways to move, breathe, and eat.

Take the latter, for example. Fish usually pucker up and suck prey into their mouths. But air is 900 times less dense than water, so land-livers must bite into their food to get a meal. Researchers at Harvard University have just completed a study that gives a clear picture of how that change was made.

“Aquatic creatures developed the tools they needed to feed on land before they completely left water,” notes Molly Markey, a lecturer on earth and planetary sciences. “Our research suggests that these first tetrapods, four-footed animals, bit on prey in shallow water or on land. Although they may have occasionally captured a meal by suction.”

To become biters, the invaders had to change their teeth and skulls, and learn to walk. Along with Charles Marshall, a professor of biology and of geology at Harvard’s Museum of Comparative Zoology, Markey compared the boney remains of a 365-million-year-old fish named Eusthenopteron, two ancient tetrapods called Acanthostega and Phonerpeton, and a modern fish. The salamanderlike Acanthostega spent much of its life in the water, Phonerpeton lived on land. Both Acanthostega and Eusthenopteron possessed lungs and gills, so they could breathe air or water, like today’s lungfishes. All three ancients boasted pointed teeth, indicating that they were meat-eating predators.