Recovered from a coal mine in the Khambhat region of Gujarat in western India, the 150-kilogram haul contains more than 700 fossilised arthropods (invertebrates with a jointed body and limbs and a hard exoskeleton) from at least 100 different species, including ancient ants, termites, bees, spiders and flies. The creatures date back to around 52 million years ago, before the collision of India and the Asian plate.

The amber provides the oldest evidence of tropical forests in Asia, tests having linked it to hardwood trees belonging to the Dipterocarpaceae family, which today make up 80 per cent of the forest canopy in Southeast Asia. More intriguingly, however, they offer evidence that a chain of islands may have linked India to the Asian mainland at the time.

India split off from Africa around 160 million years ago and then spent the next 100 million years moving towards Asia at a rate of 20 centimetres a year. This would have been long enough for arthropods trapped on the Indian landmass to evolve into a suite of unique species, but the encased organisms are closely related to Asian and European species.

‘Our findings suggest that the mixing of fauna was already so strong that it was already happening for several million years,’ said Jes Rust, a palaeontologist at the University of Bonn and one of the study’s authors. He and his collaborators suggest that the imminent collision between India and Asia may have created an arc of islands that connected the two landmasses like stepping stones.

December 2010