Raw Amber
The amber, dubbed Cambay amber, was found in lignite mines in the Cambay Shale of the Indian state of Gujarat. Jes Rust from the University of Bonn in Germany led an international team of researchers from India, Germany and the US.
According to a predominant theory of continents' formation, at first there were only two so-called supercontinents on Earth. The one in the north was called Laurasia and the other one, located more towards the south, Gondwana. When Gondwana split up into several smaller pieces in the mid-Jurassic, some 160 million years ago, most of its parts stayed in the southern hemisphere, but one started drifting towards the north. Having floated in the ocean for at least 100 million years at a remarkable rate of 15-25cm per year, it eventually collided with Asia and became what we know today as the Indian subcontinent. In the process, the Himalayas were formed.
Most of the recently discovered bugs also show links to modern insects as well as those that lived millions of years ago in different parts of the world, including Asia, Australia, and even South America. The lead author Dr Rust told BBC News that this could be explained by land-bridge connections - possibly small islands that formed before the collision with Asia, in the Eocene - between the Indian "ferry" and other landmasses.
"The Indian amber is from the Lower Eocene and was likely produced by flowering hardwood trees called Dipterocarpaceae, [trees] that predominate in the forests of Southeast Asia today," Paul Nascimbene of the American Museum of Natural History in New York said. To determine where the amber came from, the scientists chemically fingerprinted it. They also analyzed the wood anatomy of fossilised branches and trunks on the site.
"Fossil wood samples were also recovered in association with the amber, [and they] showed that these samples preserved details of the wood's microstructure, pointing to dipterocarps as the probable source," added Dr Nascimbene. The team also said that it was able to determine the age of the modern rainforest.
Up until now, many experts used to suggest that this type of tropical rainforest, found today all over the South-East Asia, first originated in the Miocene some 20 or 25 million years ago. But the recent discovery challenged that idea. David Grimaldi from the American Museum of Natural History and another co-author said that the rainforest is at least 60 million years old.
Amber looks like yellow-brownish rocks. Most of the fossil outcrops are in drier, very eroded areas of the northern hemisphere or southern parts of southern hemisphere, but not so much in the equatorial belt.
Besides the rainforest's age and India's biogeography, the most astonishing part of the discovery was the huge number of perfectly preserved specimens of insects, most of which have never been seen before.
Unlike other types of amber found in deposits in the north, the Indian amber is much softer. This unique property allowed the scientists to completely dissolve the amber using solvents - toluene and chloroform - and extract the ancient insects, plants and fungi.
"We have complete, three-dimensionally preserved specimens that are 52 million years old and you can handle them almost like living ones," said Dr Rust. "Of course they are very fragile, but it is still astonishing.
"We have several examples where it is possible to get a complete specimen out. And of course this opens a new dimension in investigations of this material. Many insects are related to modern and ancient species found in different parts of the world The researcher said that this amber deposit was the first important one found in India. "There are tonnes of amber [in this Indian deposit], and what is interesting about it is that it was produced in the tropics, the most highly diverse areas in respect to species diversity," said Dr Rust.
"And the fossil record of the terrestrial tropics is not so good, because usually all the organic material gets rotten very quickly."
With tonnes of amber at their disposal, the researcher said his team hoped to uncover many more secrets of the peculiar world that existed millions of years ago.
