Taphonomy explores post-mortem relations between organic remains and their external environment. Paleoecologists must first be taphonomists, because studies of life-environmental histories require prior knowledge of post-mortem events. Two types of post-mortem events can seriously hamper the recognition and analysis of fossil communities: (1) information losses through nonpreservation, and (2) losses through transport away from the life setting. Although many organisms are capable of leaving multiple or redundant evidence of their presence, redundancy cannot fully counterbalance the many processes leading to information losses.
At the present stage of our knowledge, in situ preservation is the only valid criterion we possess for recognizing fossil communities. Information losses through transport must be minimal in these cases; major losses occur through nonpreservation. Data on potential information losses through nonpreservation are not numerous. The available analyses of Recent marine communities indicate that from 7 to 67 percent of these communities' species are soft-bodied and have little potential for preservation. Fewer data exist concerning actual information losses for fossil communities of any type.
Actual losses can be estimated for oyster communities from the Atlantic Coastal Plain in North Carolina. An Oligocene Crassostrea gigantissima (Finch) community at Belgrade contains about 18 preserved megascopic species. Documented processes contributing to information loss included dissipation of organic soft parts and dissolution of chitinous, siliceous, and aragonitic skeletons. A Recent minimal Crassostrea virginica (Gmelin) community from the Beaufort area includes 80 megascopic animal species. This Recent community, if subjected to the same history as the fossil one, would yield similar types and amounts of preserved information. The comparative analysis suggests, therefore, that the Oligocene community contained the same major taxa as the Recent community; over 75 percent of the species in the original Oligocene community have not been preserved.