Edited sentence: Around the same time, other types of filter feeders appeared, which suggests that some change made the environment more favorable for this lifestyle.By the Mid Ordovician, about , fossils of all the modern  orders of  stenolaemates and of the ctenosome order of gymnolaemates had appeared.Fossils of about 15,000 bryozoan species have been found.Fossils of cheilosotmates, another order of gymnolaemates, first appear in the Mesozoic  era.However hardly any fossils have been found of the soft, freshwater phylactolaemates.Taxa with  mineralized skeletons appear in rocks dating from early in the Ordovician  period, which began about