THE LOWER ORDOVICIAN FEZOUATA FORMATIONS: MIXING EVOLUTIONARY FAUNAS

The Lower Ordovician Fezouata formations of Morocco yield taxa from all three “Evolutionary Faunas” (Cambrian, Paleozoic, and Modern). Members of the stem groups of higher taxa characteristic of the Cambrian, such as anomalocarids, occur alongside derived clades not otherwise known from the Early Ordovician, including xiphosurids. Thus, the assemblage offers unparalleled insights into the links between the establishment of major phyla during the Cambrian explosion and the diversification of lower-level taxonomic groups during the Great Ordovician Biodiversification Event (GOBE). We present a census of Fezouata fossils in the Yale Peabody Collections, which is compared to similar data from other Paleozoic Lagerstätten to generate a quantitative assessment of community similarity. Specifically, we use non-metric multidimensional scaling ordination and cluster analysis to examine relationships between the taxonomic composition of studied sites. We compare the extent of faunal overlap between Lagerstätten and explore whether there is more overlap in Sepkoski's Evolutionary Faunas when data from Lagerstätten are included than there is if only the normal shelly fossil record is considered. A preliminary survey of the Yale Peabody Museum collections suggests that representatives of the Cambrian Fauna make up the majority of the soft-bodied component of the Fezouata (e.g. marrellomorphs, radiodontids), while representatives of the Paleozoic Fauna comprise the shelly biota (e.g. echinoderms, gastropods). Understanding the roles of elements of the Cambrian Fauna in the ecology of the Fezouata—and the Early Ordovician in general—may impact our understanding of the evolution of Paleozoic ecosystems and offer new insights into the diversification of early life and the links between the Cambrian Explosion and GOBE.