Abstract

Bulk samples are among the foremost sources of quantitative data retrieved from the fossil record. However, such samples are not sieved in a uniform way, even among research projects with a very similar research focus. Several studies recently have demonstrated the sensitivity of paleontological patterns to changes in sieve size and underscored the importance of controlling for mesh size in paleontological analyses. Building on previous work, this study exploits a large dataset of Miocene mollusks that is fortuitously suitable for exploring the effect of mesh size: dimensions of each fossil were measured, all samples were acquired with fine screens (≤1 mm mesh), and data for numerous paleoecological and taphonomic variables were obtained for each specimen. This large dataset was sieved artificially (i.e., subsampled in computer simulations) to explore the effects of mesh size. The results show that paleontological variables, from taphonomic and paleoecological parameters to diversity indices, can fluctuate, to various degrees, as a function of mesh size. Some parameters (e.g., evenness indices) appear remarkably invariant to mesh size, while others (e.g., encrustation rate) can vary dramatically with a small change in mesh size. Most importantly, even when the compared datasets are sieved uniformly with the same standard mesh size, outcomes of comparative analyses can lead to disparate conclusions when that standard size is changed. The mesh-size sensitivity observed here for a wide assortment of paleontological patterns points to ubiquitous influence of body size on taphonomic, ecological, and evolutionary patterns and underscores the importance of developing sampling strategies and/or corrective analytical measures for making data more comparable in terms of mesh size across and within studies. Future research also should concentrate on evaluating secular trends in size-filtering aspects of extraction methods used to acquire quantitative samples throughout the Phanerozoic fossil record.

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