Phanerozoic Marine Communities

Abstract

Marine paleocommunities are time-averaged assemblages of primarily skeletal remains. Nonetheless, they do represent the communities from which they were derived. Patterns of change in marine communities reflect the major changes in faunal composition and ecospace utilization for the whole marine biota. Although species turnover is frequent, marine shelf community types persist for long intervals of time. Reef communities show great fluctuation in importance superimposed on two phases of long-term development of complexity. Community composition has been strongly influenced by an onshore to offshore displacement of faunal types through time. The onshore origins of new faunal types contrasts with the higher rates of evolutionary turnover in offshore settings. Attributes of community structure such as succession and trophic grouping can be monitored at points in the fossil record but no continuity of trends is yet well established. The elaboration of predatory life habits and the development of both active infaunal and multilayered epifaunal modes of life (tiering) characterize the changes in community structure during the Phanerozoic. Emergent properties of communities and coordinated patterns of evolutionary change (coevolution?) suggest that communities are more than epiphenomena even though their basic distribution is always dictated by adaptive responses along environmental gradients.