A study of fossil dinosaur dung has for the first time confirmed that the ancient reptiles ate grass. Grass was previously thought to have become common only after the dinosaurs died out 65 million years ago. But grasses were probably not a very important part of dinosaur diets - the fossilised faeces show the big beasts ate many different types of plants. However, the Science journal study suggests grass was possibly an important food for early mammals. Caroline Strömberg from the Swedish Museum of Natural History and her colleagues studied phytoliths (mineral particles produced by grass and other plants) preserved in fossil dinosaur dung from central India. The 65-67 million-year-old dung fossils, or coprolites, are thought to have been made by so-called titanosaur sauropods; large, vegetarian dinosaurs. "It's difficult to tell how widespread [grass grazing] was," Ms Strömberg told the BBC News website, "Dinosaurs seem to have been indiscriminate feeders." The study also sheds new light on the evolution of grass. Grasses are thought to have undergone a major diversification and geographic proliferation during the so-called Cenozoic, after the dinosaurs had gone extinct. But the researchers found at least five different types of grass in the droppings. This suggests grasses had already undergone substantial diversification in the Late Cretaceous, when the giant beasts still walked the Earth.