Chinese and Germany scientists found sponge fossils dating back more than 521 million years in central China's Hunan Province.
Luo Cui, a researcher with the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences, said the three-dimensionally preserved sponge fossils found at the Niutitang Formation in Hunan lived about 521 million years ago in the early Cambrian Period.
The fossils are kept in phosphorites, and they are believed to be among the earliest in situ preserved sponge fossils, Luo said.
"Disarticulated spicules scattered in other parts of the investigated phosphorites indicate a still unexplored diversity in the fossil community," she said.
Luo carried out the research with German researcher Joachim Reitner.
She said the findings will help researchers understand the origin and evolution of early sponge lives and multicellular organisms.
The paper was published in the PalZ, a German journal.