Extraordinary fossils solve a 500-million-year mystery: Bryozoans were there at the dawn of animal life

Fossils from 520-million-year-old rocks in China provide the first clear evidence that bryozoans were part of the Cambrian explosion. Bryozoans are tiny, filter-feeding colonial animals common in today’s oceans, but their early history has long been unclear because they did not appear in the fossil record until about 50 million years after most major animal groups. These newly discovered fossils fill that gap, showing that bryozoans emerged during the Cambrian explosion alongside other early animal groups.