NANJING - A cluster of exceptionally-preserved fauna fossils has been found in east China's Zhejiang Province, it was announced today.

The fossils may help scientists understand more about the seabed in the period around a mass extinction event that occurred at the end of the Ordovician period, which was around 443-445 million years ago.

The biota, which was discovered in Anji County in northern Zhejiang, contains over 75 sponge species, many featuring preserved soft tissue.

The sponges are believed to have played a part in the recovery of the ecosystem after the mass extinction.

The end-Ordovician extinction was the first of the five big Phanerozoic extinction events on earth. Around 85 percent of species alive at the time, which were mostly in the sea, were wiped out. Attempts to model the ecosystem of the time have failed due to limited evidence.

Archeologists have said the diversity of the Anji discovery is unprecedented for any Hirnantian fossil group, and the fauna provides a unique window into a post-extinction ecosystem.

"The discovery of Anji biota proves that there was still biological activities after the extinction and previous research indicates that sponges might have been 'ecosystem engineers' following many extinctions," said Zhang Yuandong, researcher with the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences.

The discoveries were published on the "Current Biology Journal" website by a joint team of researchers from China and Britain.