Document Type

Article

Publication Date

January 2007

Abstract

Biogeographic patterns in primarily Cambrian arachnomorph taxa are investigated using a recently constructed phylogenetic hypothesis in order to explore the biogeographic context of the Cambrian radiation. A modified version of Brooks Parsimony Analysis is employed to elucidate patterns of vicariance and geodispersal in taxa from six regions (Laurentia, Baltica, Siberia, Australia, Africa and China). Well resolved vicariance and geodispersal trees are very similar and reconstruct Laurentia and China as sister areas. This close area relationship between Laurentia and China provides extensive evidence for congruent vicariance and range expansion in Cambrian arachnomorphs, while data from trilobites do not show this pattern. Our results imply that cyclic events (such as sea-level change), in conjunction with dispersal ability, may have been more important than tectonic events in generating the biogeographic patterns we observed in Cambrian arachnomorphs. Further, the greater degree of dispersal in various non-trilobite arachnomorph lineages relative to trilobites is correlated with greater extinction resistance across the early-Middle Cambrian boundary.

Comments

This article originally appeared in Memoirs of the Association of Australasian Palaeontologists in Volume 34 and can be found online at this link.

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