WHY PALEOECOLOGY MATTERS: A CAUTIONARY NOTE FROM THE PLEISTOCENE OF FLORIDA

Organisms vary in form and behavior due to both genetics and environment . Recognizing which portion of observed variability is paleoenvironmentally -induced versus evolutionary requires an understanding of how the living organism varied from environment to environment. This can only be done in the fossil record if paleoenvironments are well understood.

To construct a paleoenvironmental framework , a high resolution paleoecologic analysis was performed on bulk sediment samples from a massive shell bed of the Pleistocene Fort Thompson Formation of Florida. At outcrop, the shell bed appeared to be homogenous. However, the paleoecologic analysis revealed two distinct fossil assemblages. These assemblages indicate that two different sets of paleoenvironmental conditions were in effect during different times of deposition of this apparently homogeneous shell bed. Morphological and paleoecologic patterns were analyzed in this paleoenvironmental framework.

Analyses of predator-prey relationships (between naticid predators and venerid prey) and epibiont-host relationships (between venerid hosts and coral and barnacle epibionts) both indicate significant differences between the two paleoenvironmental settings. Morphometric analysis of Mercenaria campechiensis indicates significant morphologic differences between samples from the two paleoenvironmental zones. The results of morphologic analysis of another clam (Chione cancellata) will also be interpreted in this paleoenvironmental framework as will geochemical, sedimentological and taphonomic analyses.

Without the paleoenvironmental framework constructed from the paleoecologic analysis the significant differences in both morphology and behavior found in these studies would not have been recognized. Thus, potentially important evolutionary and paleoecologic information would not have been found, opening the door for misinterpretation.