Washington - Traces of grass found in fossilised dinosaur dung proves that grass grew on Earth much earlier than previously thought and changes beliefs about dinosaurs' diets, a study published on Friday showed.
"This is food for thought, so to speak," researcher Caroline Stroemberg of the Swedish Museum of Natural History told AFP.
Until now, scientists believed that grass first appeared on Earth 55 million years ago, and that herbivorous dinosaurs grazed on other plants.
But together with two Indian researchers, Stroemberg discovered evidence of grasses much earlier in the coprolites, or fossilised dung, of titanosaur sauropods, large, long-necked herbivorous dinosaurs.
| 'We've always believed that Earth was grass-free at the time of the dinosaurs' |
Their findings were published in Friday's edition of the scientific journal Science.
The presence of grass during the dinosaur era was indicated by specific phytoliths, or mineral structures left behind by plants, in the coprolites found in India, the report said.
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That dated the grasses to at least 65 million years ago, the end of the Cretaceous period when the dinosaurs are believed to have died out.
The highly variegated structures of the phytoliths also reveal a much larger diversification among grasses earlier than previously thought.
However, based on the proportion of the phytoliths found in the dung, grasses apparently were not the dinosaurs' main source of food.
"We've always believed that Earth was grass-free at the time of the dinosaurs. This has always fascinated people because grass is such an important part of our ecosystem. Now we'll have to rethink a lot of things," Stroemberg said.
The evidence of early grass also suggested that the early mammals with teeth adapted to chew grassy matter could have lived alongside the dinosaurs, according to the researchers.
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