Eat your greens Jay Fleming/Getty

The bonnethead shark, a relative of the hammerhead, absorbs nutrients from the seagrass it eats, making it the first known omnivorous shark.

Biologists had previously noticed that bonnetheads consume copious amounts of seagrass in addition to crustaceans and other shellfish. But because the bonnethead’s digestive system looks almost identical to other meat-eating sharks – and so seems to be best suited to deal with a high protein diet – scientists always assumed the seagrass ingestion was accidental.

To better understand these sharks’ diet, Samantha Leigh at University of California Irvine and her colleagues fed five wild-caught …