215-4 Reconstructing Terrestrial Arthropod Feeding Dynamics in Pennsylvanian Peat Forest Using Coprolites

Session: Coprolite Happens: Insights into Geobiology

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Abstract:

Terrestrial arthropods played a central role in Pennsylvanian coal-swamp ecosystems. However, their diversity and feeding behaviors remain poorly understood due to limitations of the fossil record. Coal balls are carbonate permineralizations of peat that preserve abundant arthropod coprolites (fossilized fecal pellets) and provide direct evidence of feeding strategies, gut contents, and habitat use in these late Paleozoic wetlands. They also capture exceptionally rich floral diversity, preserving tissue with cellular-level resolution. We assembled a dataset of 5,530 coprolites from five coal members of Pennsylvanian age, from oldest to youngest, from the Illinois and Appalachian Basins: Rock Spring Coal (Pottsville Series Cross Mountain Formation; Lower Pennsylvanian seam of Eastern Tennessee), Mt. Rorah Coal (Desmoinesian Tradewater Formation; formerly known as Bald Hill Coal), the Springfield Coal (No. 5 Coal, Desmoinesian Carbondale Formation), the Herrin Coal (No. 6 Coal, Desmoinesian Carbondale Formation), and the Calhoun Coal (Berryville, Missourian Mattoon Formation). These coals span tropical lowland swamp facies from the younger Desmoinesian into the older Missourian Series and collectively preserve diverse peat‑forming environments. Each coprolite was digitally annotated for quantitative (length and width) and qualitative (shape, degree of mastication, spatial distribution, contents) attributes. Twenty morphotypes were identified from a combination of visual analysis and an unsupervised k‑prototype multivariate clustering algorithm. This characterization was further validated by a pruned decision‑tree classifier. These morphotypes exhibit four distinct feeding behaviors: detritivory, herbivory, palynivory, and coprophagy, which occur in microhabitats ranging from forest-floor litter to living and decomposing plant organs, and to canopy foliage. Potential producers were inferred by comparing morphotype characteristics with those of modern arthropods. The mouthparts and feeding behaviors of these groups were also taken into account. To quantify trophic structure, we performed network analysis on plant–coprolite and producer–coprolite associations. The plant–coprolite network reveals specialist versus generalist feeders, while the producer–coprolite network highlights keystone arthropod groups and their functional guilds. By integrating typological, multivariate, and network approaches, our analysis demonstrates that coprolites preserve high‑resolution ecological and behavioral data absent from the body‑fossil record. Coprolites are an indispensable trace fossil for reconstructing Pennsylvanian age arthropod–plant interactions and offer new insights into functional diversity, trophic complexity, and ecosystem dynamics in late Paleozoic peat forests.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-6593

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