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

Bryozoans are tiny, filter-feeding colonial invertebrates that thrive in the world's oceans today, yet for decades their origins presented a puzzling gap in the fossil record. While nearly every other major animal group made its first appearance during the Cambrian explosion roughly 530 million years ago, the bryozoan fossil record remained stubbornly silent until the Ordovician period, some 50 million years later.