Rare Fossils Discovered in Shaanxi Confirm Bryozoans Originated in the Early Cambrian

A Chinese research team recently discovered a batch of wellpreserved microscopic bryozoan fossils in early Cambrian strata in Hanzhong, southern Shaanxi, China. The findings were published online in the international academic journal Nature on the evening of June 3, Beijing time. The study shows that these fossils preserve both mineralized skeletons and in situ soft tissue. Using a range of techniques, including acid etching, scanning electron microscopy, energydispersive spectroscopy, and Xray tomography, the researchers confirmed that they belong to a group within the gymnolaemate class of the phylum Bryozoa. Phylogenetic analysis indicates that the relevant lineage had already diverged in the early Cambrian. This discovery pushes back the fossil record of bryozoans with mineralized skeletons from the Ordovician to the early Cambrian, by at least about 50 million years, and also provides key evidence for the longdebated question of bryozoan origins.