Data from: The Fezouata Shale Formation biota is typical for the high latitudes of the early Ordovician – a quantitative approach

The Fezouata Shale Formation has dramatically impacted our understanding
of early Ordovician marine ecosystems before the Great Ordovician
Biodiversification Event (GOBE), thanks to the abundance and quality of
exceptionally preserved animals within. Systematic work has noted that the
shelly fossil sub-assemblages of the Fezouata Shale biota are typical of
open-marine deposits from the Lower Ordovician, but no studies have tested
the quantitative validity of this statement. We extracted 491 occurrences
of recalcitrant fossil genera from the Paleobiology Database to
reconstruct 31 sub-assemblages, to explore the paleoecology of the
Fezouata Shale and other contemporary, high-latitude (66°S – 90°S)
deposits from the Lower Ordovician (485.4 Ma – 470 Ma) and test the
interpretation that the Fezouata Shale biota is typical for an Ordovician
open-marine environment. Sørensen’s dissimilarity metrics and Wilcoxon
tests indicate that the sub-assemblages of the Tremadocian-aged lower
Fezouata Shale are approximately 20 percent more heterogenous than the
Floian-aged upper Fezouata Shale. Dissimilarity metrics and visualization
suggests that while the lower Fezouata and upper Fezouata share faunal
components, the two sections have distinct faunas. We find that the faunal
composition of the lower Fezouata Shale is comparable with other
Tremadocian-aged sub-assemblages from high latitudes, suggesting that it
is typical for an early Ordovician open-marine environment. We also find
differences in faunal composition between Tremadocian- and Floian-aged
deposits. Our results corroborate previous field-based and qualitative
systematic studies that concluded that the shelly assemblages of the
Fezouata Shale are comparable with those of other Lower Ordovician
deposits from high latitudes. This establishes the first quantitative
baseline for examining the composition and variability within the
assemblages of the Fezouata Shale which will be key to future studies
attempting to discern the degree to which it can inform our understanding
of marine ecosystems just before the start of the GOBE.