Major adaptive radiation of cheilostomate bryozoans in Upper Cretaceous might be triggered by an origin of larval brooding. Most important consequences of this event were (1) a decrease in oocytic production, (2) a shortening of terms of larval development, (3) an abandonment of planctotrophic larvae, (4) a decline in larval dispersion. We suggest that the origin of brooding and, as a result, short-living lecithotrophic larvae have led to a decrease of gene flow between distant populations, and hence intensified the allopatric and quasi-sympatric (parapatric) speciation in Cheilostomatida.