Data from: Breaking down the lithification bias: the effect of preferential sampling of larger specimens on the estimate of species richness, evenness, and average specimen size

Lithification, the transition of unconsolidated sediments to fully
indurated rocks, can potentially bias estimates of species richness,
evenness, and body size distribution derived from fossil assemblages.
Fossil collections made from well-indurated rocks consistently exhibit
lower species richness, lower evenness, and a specimen size distribution
skewed towards larger specimens relative to collections made from
unconsolidated sediments, even when collections are drawn from the same
assemblage. This phenomenon is known as the lithification bias. While the
bias itself has been demonstrated empirically, much less attention has
been paid to its causes. Proposed causes include taphonomic processes
(e.g., destruction of small specimens during early diagenesis) or
methodological differences (e.g., sieving vs. counting specimens on
outcrops, bedding surfaces, or mechanically split surfaces). Here we
investigate the potential effects of preferential intersection that could
also result in a methodologically related bias: the preferential sampling
of larger specimens relative to smaller ones when fossils are counted on
rock surfaces. We used an analog model to simulate preferential
intersection (fossil collection via splitting fossiliferous rock) and
compare the results to a random draw model that approximates the effects
of sieving. The model was parameterized using nine different combinations
of species abundance and species size distributions. The results show
that, with rare exceptions, species richness is 5–23% lower, evenness
5-25% lower, and average specimen size 24–150% higher in preferential
intersection than in random draw simulations. We conclude that
preferential intersection can impose a significant bias independent of
other mechanisms (e.g., preferential destruction of smaller specimens
during diagenetic or sampling processes), that the magnitude of this bias
is partially dependent on the species abundance and size distributions,
and that this bias alone does not fully account for empirically observed
lithification bias on species richness (i.e., other sources of bias are
also at work).