fossil bryozoans first appear in the early ordovician and had a huge adaptive radiation. they were abundant throughout the palaeozoic era: they were one of the most dominant groups of palaeozoic fossils. they were major components of seabed communities and, like modern-day bryozoans, played an important role in sediment stabilization and binding. they were food sources for many other benthic organisms. during the lower carboniferous (mississippian) 354 to 323 million years ago, bryozoans were so common that their broken skeletons form entire limestone beds.