"Somewhere, something incredible is waiting to be known" Carl Sagan
sábado, 24 de septiembre de 2011
Palaeontology - Dinosaur diet throws light on rice in India
Tiny plant particles embedded in dinosaur dung from central India suggest that dinosaurs were eating rice more than 65 million years ago and that rice had emerged on Earth much earlier than hitherto believed.
Fossilised dung of a titanosaur, (above) tissues of plants in the fossilised dinosaur dung [Credit: Telegraph/India]
A team of scientists from India, China and the US has shown that the plant particles made up of silica are the residues of wild varieties of rice remarkably similar to the silica particles found in the leaves of modern wild rice.
The findings, published on Monday in the journal Nature Communications, have stirred speculation in scientific circles that rice may have originated in India before it dispersed across Asia.
“This is the oldest record of rice in the world,” said Vandana Prasad, a scientist at the Birbal Sahni Institute of Paleobotany, Lucknow, and a team member who compared the silica particles from the dung and the leaves of modern wild rice using high-power microscopes.
Over the past decade, palaeontologists have recovered hundreds of samples of dinosaur dung from ancient flood plains close to Pisdura village near Nagpur. Six years ago, Prasad and her colleagues had identified grass residues in the dung, the first evidence that dinosaurs had consumed grass. “The new evidence suggests that while consuming a variety of plants and grass, some dinosaurs may also have consumed rice,” Prasad told The Telegraph.
The researchers believe the dung belonged to large herbivores called titanosaurs.
The contents of the dung suggest that dinosaurs were picky eaters. “We see a far greater variety of fossilised plant residues in the surrounding sediments than what we find in the dung,” said Dhananjay Mohabey, a palaeontologist with the Geological Survey of India, Nagpur. “It looks like the herbivores preferred soft plant tissues and avoided hard and woody plant parts,” Mohabey said.
Some scientists believe the new findings may change existing ideas about the origin and evolution of rice. Groups of international scientists have used genetic analysis to suggest that wild rice originated about 25 million years ago in eastern Asia.
The study indicates the presence of wild rice in India before the demise of the dinosaurs 65 million years ago, and at a time when India was south of the equator, having just broken off from Madagascar and was an island subcontinent moving northward.
“This raises the possibility that rice was growing in India before it collided with Asia,” said Ashok Sahni, a palaeontologist at the University of Lucknow, another team member. “Rice and other grasses may have dispersed into Asia after the collision.”
The similarities in the fine microscopic signatures of silica particles from the dinosaur dung and the leaves of modern wild rice are striking. “This suggests that rice species has been in an evolutionary stasis,” Sahni said.
The Lucknow scientists collaborated with researchers at the Geological Survey of India, Nagpur, in processing the dinosaur dung. Chinese collaborators lent the Indian scientists samples of modern wild rice for comparison with the silica particles in the dung. The US scientists who collaborated in the study have been trying to piece together the history of the earliest of wild grasses.