Abstract
AbstractRecent excavations of Ediacaran assemblages have revealed striking bed-to-bed variation in diversity–abundance structure, offering potential insight into the ecology and taphonomy of these poorly understood early Metazoan ecosystems. Here we compare faunal variability in Ediacaran assemblages to that of younger benthic assemblages, both fossil and modern. We decompose the diversity of local assemblages into within-collection (α) and among-collection (β) components and show that β diversity in Ediacaran assemblages is unusually high relative to younger assemblages. Average between-bed ecological dissimilarities in the Phanerozoic fossil record are comparable to within-habitat dissimilarities typically observed over meter to kilometer scales in modern benthic marine habitats, but dissimilarities in Ediacaran assemblages are comparable to those typically observed over 10–100 km scales in modern habitats. We suggest that the unusually variable diversity–abundance structure of Ediacaran assemblages is due both to their preservation as near snapshots of benthic communities and to original ecological differences, in particular the paucity of motile taxa and the near lack of predation and infaunalization.
Highlights
Ediacara-type fossil assemblages, known from nearly 40 million years before the Cambrian explosion of skeletonized metazoans, include a diverse suite of globally distributed, exceptionally preserved, macroscopic, morphologically disparate soft-bodied organisms that are largely absent from the post-Ediacaran record (Narbonne 2005; Xiao and Laflamme 2009; Droser and Gehling 2015)
Understanding the ecology of Ediacarans is complicated by the unusual mode of preservation of most Ediacaran assemblages as casts and molds in earlycemented sandstones (Tarhan et al 2016)
As is expected given the absence of softbodied taxa in most fossil assemblages, Phanerozoic fossil data sets have significantly lower α diversity than modern data sets
Summary
Ediacara-type fossil assemblages, known from nearly 40 million years before the Cambrian explosion of skeletonized metazoans, include a diverse suite of globally distributed, exceptionally preserved, macroscopic, morphologically disparate soft-bodied organisms that are largely absent from the post-Ediacaran record (Narbonne 2005; Xiao and Laflamme 2009; Droser and Gehling 2015). One of the most striking observations to emerge from this work is that successive beds exhibit little sedimentological variation but substantial variation in diversity–abundance structure (Droser and Gehling 2015; Droser et al 2017). If this variability is truly unusual in the context of younger assemblages, it might offer insight into the ecology and/or taphonomy of benthic
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