RESIDUAL COLOR PATTERNS IN EOCENE ATHLETA (GASTROPODA:VOLUTIDAE) FROM THE US GULF COASTAL PLAIN

Many extant members of the class Gastropoda display color patterns on their shells that are unique to their particular species. While there may be some intraspecific variation in the details of shell color patterns, distinctive underlying elements that unify species are commonly present. In the vast majority of fossil shells, pigments have deteriorated or disappeared completely to the human eye. Hidden patterns may be enhanced or revealed by bleaching the shells in a dilute solution of household bleach and water and viewing them under ultraviolet (UV) light. Previous work by Pacaud and Pons (2013) on French and British Athleta has established the existence of a previously unknown species (A. yvonnae) based only on distinct color pattern differences. Here we aim to determine if residual color patterns can be used as a character by which to discriminate various fossil species of the genus Athleta from Eocene deposits of the US Gulf Coastal Plain from one another. If bleaching fossil species of Athleta causes them to display remnant color patterns when placed under UV light, and these remnant color patterns are similar for members of the same morphospecies, yet different between morphospecies, then residual color patterns will be considered a species-level trait consistent with the preexisting morphospecies designation. On the other hand, if these remnant color patterns show multiple color pattern morphs within a single morphospecies, one may conclude the possible existence of two or more cryptic fossil species. In all, eight species of Athleta from Eocene strata in the Gulf Coastal Plain were subject to the bleaching treatment and photographed under UV light. Following the treatment, we were able to document residual color patterns in multiple specimens of all eight species. It was determined that different morphospecies of Athleta exhibit different color patterns and that the patterns can be categorized as dashes, bands, streaks and/or blotches. Some species shared residual color patterns. For example, Athleta symmetrica, A. sayanus, and A. clayi all displayed a similar pattern of thin spiral bands in varying degrees of coverage. Further phylogenetic implications will be discussed.