186-3 Examining the Functional Morphology of a Soft-Bodied Hydrozoan, *Plumalina* Hall, 1858, from the Northern Appalachian Basin Using Computational Fluid Dynamics

Session: New Approaches to Old Fossil Collections (Posters)

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Abstract:

Soft bodied fossils provide valuable insight into major components of ancient ecosystems that are not commonly preserved due to a lack of mineralized hard parts. Plumalina Hall, 1858 is a soft-bodied hydrozoan with fossil remains found abundantly in Middle through Late Devonian siliciclastics of New York State. Despite initial discovery in the mid-19^th century, the details of their ecology, especially relative to hydrozoans across the Phanerozoic and today, remain largely unexplored. The aim of this study is to use computational fluid dynamics (CFD) to evaluate the functional ecomorphology of Plumalina from the Northern Appalachian Basin. Morphological investigations are conducted on museum specimens from collections at the New York State Museum and Paleontological Research Institution. Direct measurements of these samples are used to create 3-dimensional models of the geometry of individual ‘fronds’. Further, we will reconstruct colonies based on observations of in situ bedding planes in the field and relatively large samples with hundreds of individuals housed in museum collections. These models are analyzed to evaluate the performance of observed morphologies in varied paleoenvironmental conditions (i.e. flow conditions), guided by sedimentological observations. Preliminary data indicate that Plumalina found in higher energy depositional environments, as indicated by larger grain size, are characterized by larger individual frond widths and less dense packing of fronds within a community. These morphology of these larger fronds likely results in lower drag coefficients when compared to smaller, denser forms. Additional morphological adaptations to reduce relative hydrodynamic resistance may also include decreasing hydrocladial density. Future work will utilize CFD analysis in a wider range of experimental environmental conditions and include additional colonial geometries to further refine model parameters and interpretations.

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

doi: 10.1130/abs/2025AM-10421

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