Fig. 6
Bubble plot showing network centrality scores for stratigraphic index fossils. Each bubble represents an Ediacaran macrofossil genus or ichnogenus in the bipartite network of Ediacaran formations and taxa (Fig. 4). Their colors correspond to biozones in that network (Fig. 4a, b). The diameter of each bubble equals the number of formations that contain fossils of the taxon. The x- and y-axes are node centrality scores. A node’s centrality score indicates its relative importance within a network. These scores were calculated from the taxa projection of the bipartite network based on two different definitions of centrality. The x-axis is degree centrality (or simply degree), which is the number of unique links between the taxon and any other. The scores in this plot do not reflect self-loops (i.e., connections between nodes and themselves). Whereas taxa with high degree centrality cooccur with a multitude of others, those with low scores cooccur with relatively few. The y-axis is betweenness centrality, which equals the number of shortest paths that pass through the node in its network. Whereas taxa with low betweenness centrality scores tend to be located at the beginning and end of paths, those with high scores commonly act as bridges for the flow of information. With regard to this plot, the best index fossils are red or blue (i.e., closely associated with one biozone) and have large bubbles and high centrality scores because they are geologically widespread and relatively common. Notable Terminal Ediacaran index fossils have black borders. Source data are provided as a Source Data file
