BREAKING BIVALVES: VALVE DURABILITY AND ITS EFFECT ON PALEONTOLOGICAL FIDELITY.

Paleontological fidelity, the faithful archiving of ancient source biota, is a key component of paleontological analyses, however, preservational biases, like size or skeletal durability, create barriers to fossilization, and therefore an incomplete ecological picture. Mollusks tend to have higher time-averaging compared to other benthic marine organisms like echinoids, however limited studies have been conducted exploring how variations in skeletal durability affects preservational fidelity across taxonomic groups. Mollusks collected from surficial seagrass sediments off of the Gulf Coast of Florida were analyzed to identify potential biases in skeletal durability and size across twenty-one bivalve taxa. Force data, measured in Newtons, was generated using a standing crushing device with a flat head, in order to quantify valve durability. Significant variability in shell strength was observed between species, although some exhibited comparable levels of variation among individual specimens. Intraspecific differences in shell strength were influenced by environmental factors, including chemical or biological encrustation, physical weathering, prior breakage, and drill holes. 237 specimens, divided into four predetermined size classes, revealed a strong correlation between shell thickness and durability. In contrast, other morphological traits, such as length, width, and height, showed little to no significant relationship with species abundance or skeletal mechanical strength. These results indicate that shell strength has minimal influence on species abundance in the modern seagrass-associated bivalve fossil record. The absence of a clear link between abundance and fragility suggests that the relative abundance of fossil mollusks reflects ecological factors rather than taphonomic processes