Abstract
Benthic communities can be regarded as open systems. The ecological and evolutionary behavior of a benthic community must be made clearly distinct from those of its constituent populations. Longevity of community structures through geological (or evolutionary) time appears to be related to virtual eurytopy of the constituent species populations and elasticity of the structures themselves. There is no single, major controlling factor to be found in characteristics of ecological communities, responsible for the ability of their structures to resist long-term environmental changes in geological time. [Tancredia and Ophiomorpha are discussed.].