World's oldest primitive animal fossil found in China

Washington: Scientists have discovered the “earliest and most credible” primitive animal fossil in 600 million-year-old rocks in southwest China. Researchers have found the fossil in southwest China's Guizhou province. The fossilised animal, slightly more than 1.2 mm wide and 1.1 mm tall, displays many characteristics of modern adult sponges, according to an analysis based on advanced imaging techniques.

The specimen is composed of hundreds of thousands of cells, and has a structure consisting of three adjacent hollow tubes sharing a common base, the researchers said. Flat tile-like features on the fossil's external surface, punctuated with small pores, resemble pinacocytes on modern sponges, whereas the fossil's inner surface is covered with a regular pattern of uniform pits, with many pits surrounded by collars, similar to sponge choanocytes.