Sydney, October 5 : A new study has determined that the world's worst mass extinction 250 million years ago was the trigger for a fungus explosion, which puts to rest the idea that an asteroid impact may have had a hand in the massive destruction.

When the worldwide extinction took place, lush forests lay in ruins all across the supercontinent Pangea.

In their place, fungus ruled the land, feasting on defunct wood, spreading across the planet in an orgy of decay.

According to a report by ABC News, the finding offers evidence against an alternative theory that rampant algae fed off the dead forests and puts to rest an old idea that an asteroid impact may have had a hand in the massive destruction.

"This fungus was a disaster species, something that perhaps enjoyed the extinction a little more than it should," said Mark Sephton of Imperial College London. "It proliferated all over the globe," he added.

Sephton and a team of researchers studied rocks containing microscopic fossils from the extinction.

They were trying to settle a decades-old debate: Were the remains in fact the fungus Reduviasporonites, or algae, as had previously been thought?

Carbon isotopes within the fossils indicated the organisms ate wood while they were alive, a strong sign that they were fungus.

"What we're looking at is a lot of plant die-offs concentrated in time," said Dr Peter Roopnarine of the California Academy of Sciences in San Francisco.

"We're most likely looking at episodes of intense greenhouse warming, and chemical changes in the atmosphere that made it unsuitable for the huge, massive forests living at the time," he added.

The finding has important implications for the Permian-Triassic extinction, which wiped out a large majority of life on the planet. If the fossils had turned out to be algae, it would've suggested a soggy, swampy world dominated by gradual changes in climate and the environment.

But in this ancient murder mystery, fungus fits.

It further puts to rest the idea that an asteroid impact caused the destruction.

"Fungal presence starts to increase just before the main extinction; it's not as sudden as the Cretaceous-Tertiary extinction (which killed the dinosaurs)," said Sephton.

"The idea of a declining ecosystem doesn't exactly fit will with an extraterrestrial impact event," he added. (ANI)