Chinese researchers have recently unearthed a well-preserved large sponge fossil that dates back to approximately 540 million years ago in the city of Changde, central China's Hunan Province, according to the Hunan Museum of Geology.

Described as a rare finding from the early Cambrian era, this sponge fossil holds immense scientific significance, offering invaluable insights into the early evolution of sponge animals, said Tong Guanghui, an associate researcher at the museum.

Measuring 4 cm in height and 3.5 cm in width at its broadest point, the sponge fossil exhibits a remarkable state of preservation, with the entire framework composed of siliceous spicules on the slate being meticulously conserved, he said.

"The discovery indicates that the ocean at that time already possessed a high level of primary productivity, with abundant planktonic organisms capable of supporting the survival of large sponges," he said. "It is probably that numerous other species also inhabited the ocean during that period, and future field investigations may confirm this speculation."

As the most primitive multicellular animals, sponges have appeared in the Earth's oceans approximately 600 million years ago. They attach themselves to sediments on the seabed, obtaining food from the seawater that flows past them.