ASSESSMENT OF PENNSYLVANIAN BENTHIC PALEOCOMMUNITY STRUCTURE THROUGH BIOVOLUME ANALYSIS

The Late Paleozoic Ice Age, a glacial interval spanning the late Devonian to the Permian, was an interval of rapid climatic changes coinciding with the formation of the supercontinent of Pangaea. During this time, initial cooling was followed by repeated glacial-interglacial cycles resulting in a global climate that is thought to have favored generalist taxa over more specialized genera in the marine realm. While it has long been postulated that this climactic cycling led to decelerated speciation and extinction rates globally, previous research into marine community composition focused heavily on single clades where individuals are easily quantified, such as the brachiopods, and exploration of whole community structure was limited. Counts of individuals for crinoids and bryozoans, in particular, are often difficult due to post mortem disarticulation and a colonial lifestyle, respectively. The aim of this study is to quantify the benthic community composition and biomineral productivity of the Pennsylvanian-aged benthic community represented within the Keechi Creek Shale member of the Mineral Wells Formation in Palo Pinto County, Texas. Specimens were sieved from a random subsample of an ecological bulk sample taken in situ from the outcrop. Specimens > 5 mm were selected for analysis. Taxa were identified to the genus level and classified into distinct ecoguilds based on mobility, substrate tiering, and locomotion by referencing paleoecological assignments from Paleobiology Database (paleobiodb.org). Biovolume estimates are calculated using fossil mass and volumet o account for skeletal productivity of the community, serving as a proxy for occupation of thev arious ecoguilds and trophic levels of an ecosystem. Shannon’s Diversity index and Simpson’s Dominance Index scores were then calculated for both sites, and the diversity scores were statistically compared. The resulting data suggests a shift in tiering ecoguild occupation from intermediate epifaunal to upper-epifaunal life modes up section. Future work will involve extraction and analysis of bulk samples from Missourian and Virgilian deposits.