DISTRIBUTION OF BRYOZOAN GROWTH HABIT CHARACTERISTICS IN JACKSONIAN (LATE EOCENE) FACIES OF THE GULF COAST

Bryozoans are an important component of the benthic marine fauna in a variety of environments throughout much of the Paleogene of the Coastal Plain of southeastern United States. In general, correlation exist between colony growth forms of some bryozoans and the environmental conditions in which the organism lived allow for the possibility of paleoenvironmental analyses based on skeletons alone. A new approach to bryozoan colonial growth habit analysis (originally developed with modern material) is applied here for the first time to diverse fossil faunas in order to evaluate its viability. This method differs from previous approaches to bryozoan growth form analysis in that it is a classification of growth habit characteristics rather than a classification of morphological groups. The bryozoan data set of Cheetham (1963) from the eastern Gulf Coast Jacksonian strata (164 cheilostomate species; 130 sample sites; assigned to four major biofacies) is reevaluated using non-metric multidimensional scaling (NMS) and canonical correspondence analysis (CCA). This approach provides a common ground for systematic comparison of character states among bryozoan growth habits and allows for the evaluation of relationships among morphological characters and environmental conditions in which they develop. Twenty-one unique growth habits have bee recognized, with the most common being, (1) encrusting, cemented, rigid, oligoserial, unilaminate, sheet, with no secondary skeletal thickening or branching; (2) erect, cemented, rigid, oligoserial, bilaminate, straight branches with convex surfaces, Infrequent branching in a single plane, with no branch connections or secondary skeletal thickening; and (3) erect, cemented, rigid, oligoserial, quadrate, solid, straight cylinder branches, frequent branching in a single plane, with no branch connections or secondary skeletal thickening.