科学美国人60秒:Early Land Animals Lacked Good Bites

What had the legs of a ‘gator and the jaws of a fish? Why, the earliest land animals. Because a new study shows that animals evolved weight-bearing limbs long before they had the chompers to really take advantage of a terrestrial diet. The research is in the journal Integrative and Comparative Biology. [Philip S. L. Anderson, Matt Friedman and Marcello Ruta, Late to the Table: Diversification of Tetrapod Mandibular Biomechanics Lagged Behind the Evolution of Terrestriality]

Scientists had suspected that the first four-legged creatures to haul their carcasses out of the ocean didn’t belly up to the salad bar straight away. But they lacked definitive proof.

Now, researchers have carefully examined the fossilized faces of 89 beasties that lived on land and sea some 300 [million] to 400 million years ago. They probed the jaws for a range of biomechanical features, such as how much force they could give to their bite. The result: seems it took tens of millions of years after setting foot on land to come up with a mouth that could munch on the greenery. 

Why the lag? Could be the critters had to stop being such mouth breathers and shift from using gills to using lungs, which freed their jaws to develop in new ways. And which left no more excuses to not eat their veggies.

—Karen Hopkin