The analysis of diversity partitioning is a potential tool for detecting the factors that control taxonomic diversification in a given ecological context. Previously proposed models provide a theoretical framework that is herein applied to three sets of level-bottom communities representing different phases of the Jurassic diversification of marine life. The analysis shows that mean alpha-diversity remained surprisingly constant through most of the Jurassic, whereas beta-diversity increased by a factor of 2.6 during the same time interval. Diversification that is primarily driven by increasing beta-diversity is indicative of late diversification phases in ecosystems with low interspecific competition and/or high predation, as typical for marine level-bottom communities. Although generality of this conclusion is not claimed because of data limitations, the example demonstrates that the study of diversity partitioning provides a promising approach to the basic question about the factors that control the diversification of life.