OLDEST RECORD OF FRESHWATER FISH FROM THE SOUTHERN APPALACHIANS: ICHTHYOFAUNA OF THE EARLY PLIOCENE GRAY FOSSIL SITE, NORTHEAST TENNESSEE

The Gray Fossil Site (GFS), located in northeast Tennessee, preserves an early Pliocene lacustrine environment that records a rich flora and vertebrate fauna. Fossils of fish are incredibly common at GFS with thousands of specimens representing hundreds of individuals recovered to date. Comparison with extant taxa reveals a depauperate fish fauna consisting of only two species: Lepomis sp. and Micropterus sp. GFS Micropterus resemble M. nigricans and M. dolomieu, but do not appear readily referable to either species. GFS Lepomis are highly variable in morphology, possibly a result of hybridization or relaxed selection. This assemblage contrasts sharply with modern diversity of freshwater fish in the Southeast United States. The absence of fishes that are ubiquitous in modern stream ecosystems in the region (e.g., cyprinids, catostomids) suggests no perennial surface hydrologic connection between the Gray Fossil Site pond and nearby fluvial systems. Limited opportunities for dispersal into the pond and deleterious conditions such as eutrophy, high competition, and predatory pressure may have resulted in this extremely low diversity. Articulated and partially articulated GFS fish specimens show mild to moderate degrees of post-mortem disarticulation, suggesting slowed decay and minimal scavenging likely attributable to cool water temperatures and/or anoxic conditions within the hypolimnion. Despite low diversity, the GFS ichthyofauna is the first pre-Pleistocene freshwater fish record from the Southern Appalachians and one of only a handful of similarly aged sites in eastern North America. Further comparison with extant taxa may help to elucidate the evolutionary history of centrarchids in the southeastern United States.