EVALUATING THE ECOLOGICAL ARCHITECTURE OF MAJOR EVENTS IN THE PHANEROZOIC HISTORY OF MARINE INVERTEBRATE LIFE

Paleoecological changes associated with Phanerozoic mass extinctions a nd radiations can be categorized into four nonhierarchical, nonadditiv e levels. First-level changes include colonization of a new ecosystem. Structural changes within an established ecosystem represent the seco nd level, changes within an already established ecological structure a re the third level, and taxonomic changes within a community represent the fourth level. Applying these levels to the Ordovician radiation, end-Ordovician extinction and Silurian recovery, as well as the end-Pe rmian extinction and Triassic recovery, demonstrate that paleoecologic al changes associated with these major events can be evaluated and com pared in a more rigorous manner than previously done. Results of this analysis demonstrate that use of these levels indicates that the relat ive magnitude of an event as measured by taxonomic criteria may be dec oupled from its paleoecological significance.