Late Palaeozoic biogeographic bipolarity revisited: parallel evolution, vicariance or transoceanic dispersal?

SHI GUANG R.; TABOADA ARTURO C

Brisbane

Congreso; 34th International Geological Congress; 2012

International Union of Geological Science

Strong bipolarity has been noted in Late Palaeozoic global biogeography. Existing models proposed to explain this remarkable deep-time biogeographic feature tends to emphasise the role of tectonic vicariance and transoceanic dispersal. Other models are available but limited. This study is built on recent discoveries of well preserved Carboniferous-Permian bipolar brachiopod taxa from Argentina. As an alternative interpretation, here we propose a new scenario based on our detailed taxonomic study of two separate, but morphologically similar, lineages of Late Palaeozoic productoid brachiopods. It appears plausible that the morphological similarities between a lineage of Late Palaeozoic Argentinean brachiopod genera, ranging from Lanipustula through Verchojania to Jakutoproductus, and that of the same lineage from Siberia (Verchoyansk Mountains), could be a consequence of parallel evolution, although trans-oceanic dispersal as a mechanism of initiating and sustaining the Late Palaeozoic bipolarity remains a viable scenario. If parallel evolution was indeed the mechanism, it would most likely have been preceded by a transoceanic dispersal stage during the late Viséan global cooling allowing some cool-water brachiopod taxa migrating from the northern hemisphere to Gondwana. Once established in Argentina, these 'northern hemispheric' taxa then went through a process of parallel evolution in the local environment, leading to the formation of a lineage of brachiopod genera over time. It is interesting to note that the parallel lineage thus far has only been noted to be shared between Argentina and Siberia. The reason for this remains unclear, although several possibilities will be discussed.