SHIFTING BIOGEOGRAPHIC PROVINCES ACROSS THE PROTEROZOIC-CAMBRIAN BOUNDARY

Cambrian fossil assemblages show well-defined global biogeographic provinces, created in part by continental rifting and separation during this interval. Assemblages of trilobites, archaeocyaths, and shelly fossils all show significant division into provinces. The latest Proterozoic "Ediacara biota" also shows three spatially contiguous assemblages that have been called biogeographic provinces. These three assemblages were also probably distinct in time, and may result from faunal succession in time as much as from geographic separation. Nonetheless, a number of regions with closely related Ediacaran assemblages, such as Namibia and southwestern North America, or Australia and Baltica, have Cambrian assemblages that fall into completely different provinces. Increasingly precise dating and correlation of many fossil assemblages allows the development and succession of biogeographic provinces to be studied at finer temporal resolution. I will present parsimony analysis of endemism (PAE) area cladograms as a first approximation to a general hypothesis of why and how old provinces were replaced by newer ones.