Chapter 4 Global distributional dynamics of Cambrian clades as revealed by Burgess Shale-type deposits

The Cambrian geographical and temporal distributions of many clades remain poorly understood, despite their importance for elucidating the palaeobiogeographical context of the Cambrian radiation. New species and genus level occurrence databases were developed to analyse temporal and geographical distributional patterns in taxa belonging to 14 clades from over 60 globally distributed early and Middle Cambrian Burgess Shale-type lagerstätten. Analyses demonstrate that clades with confirmed Precambrian origins were, on average, more widespread and temporally persistent than clades with first fossil occurrences in the Cambrian. Despite their dominance in diversity, arthropods were less widely distributed and temporally persistent than many other groups. Finally, a significant correlation between geographical range and temporal persistence is demonstrated, supporting the hypothesis that Cambrian taxa with wider geographical ranges were less likely to go extinct than those with narrower ranges.