580


BOAG ET AL.


second test of assemblage validity. Average- linkage clustering (Kulczynski similarity) using the function hclust was performed on the diversity matrix in the R package Vegan (Oksanen 2015), resulting in a cluster dendro- gram that provided good agreement with our NMDS ordination plot. Cophenetic correlation for the dendrogram, which measures the similarity between original locality diversity dissimilarity and dissimilarities estimated by the dendrogram tree, was high (0.8418), indi- cating this analysis is a reliable alternative method for interpretation of faunal assem- blages. Only five localities ([Nil_mf], [Fitz], [SBf_Nor1], [SecA_CC], [Ferry]) changed assemblage designation between the NMDS method and cluster analyses (Fig. 2; see Supplementary Fig. S.3 for alternative cluster- ing method). Our updated taxonomic ordination and


cluster analysis supports the original conclu- sion that the localities set out in Waggoner (2003) provide fairly robust approximations of taxonomic diversity within the current Ediacaran macrofossil record and appear to remain as coherent, distinct faunal associations. However, emerging heterogene- ities exist and will likely grow as worker effort increases diversity in novel localities (Supplementary Fig. S.3). As such, these data reinforce previous studies, which have locally identified the nonrandom distribution


of Ediacaran taxa (Grazhdankin 2004; Gehling and Droser 2013). The need to statistically test the underlying factors controlling Ediacaran macrofossil distribution is therefore imperative moving forward, as they are likely to inform as to the underlying mechanisms that produce both traditional and novel biotic assemblages.


Taphonomic Biases—Preserving Lithology


Decoupling Preserving Lithology with Moldic Preservation


Taphonomic biases can influence any quanti-


tative paleontological study; this concern is heightened when dealing with exceptional soft-tissue preservation (Briggs 2003). Several taphonomic windows were open during the Ediacaran Period (Kenchington andWilby 2014), preserving macrofossils in a range of sedimento- logical facies and depositional environments, albeit in highly disproportionate regularity. We aimed to resolve whether any large-scale lithological barriers are present in order to (1) assess the impact on the overall fidelity of the taxonomic record and (2) constrain any potential lithological dependencies guiding the known Ediacaran taphonomic windows. Due to a combination of unique paleoenvir-


onmental conditions, microbially induced moldic “death masks” of soft tissues in


FIGURE 2. Average-linkage hierarchical cluster dendrogram (Kulczynski similarity) of 86 Ediacaran localities generated from the binary faunal catalogue. Assemblage rectangles (Nama, Avalon, Algae, White Sea) were plotted using function rect.hclust, which cuts the dendrogram into n closest clusters.


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