QUANTIFYING THE MORPHOLOGY AND RECONSTRUCTING THE PHYLOGENY OF VENERICARD BIVALVES ALONG THE GULF COASTAL PLAIN DURING THE PALEOCENE AND EOCENE
Planicostid venericards are abundant, diverse, and often well-preserved throughout the Paleogene units of Alabama and Mississippi. We collected specimens from eleven field sites in Alabama and Mississippi and augmented these with specimens from the Smithsonian Museum of Natural History, the Virginia Museum of Natural History, the Paleontological Research Institute, and the Mississippi Department of Environmental Quality. Species examined include Venericardia alticostata, V. wilcoxensis, V. planicosta, V. turneri, V. bashiplata, V. nanaplata, V. claiboplata, V. hatcheplata, V. densata, V. aposmithii, and V. mediaplata. We digitized images of venericards in lateral orientation and quantified venericard morphology using thirteen prominent landmarks, distributed along the beak, hinge, adductor muscles, and shell outline. We then reconstructed the phylogeny using 39 characters compiled for 11 ingroup and 4 outgroup taxa. Planicostid venericards have received relatively little taxonomic attention in the past and this research will contribute significantly to our knowledge of venericard systematics. We then qualitatively compared morphological and phylogenetic patterns with paleoclimate data across this interval to explore the evolutionary response of planicostid venericards to climate change. Preliminary results indicate that traditional species designations in this clade appear to be supported by morphometric analysis.