Argentinean-Siberian Late Palaeozoic marine biogeographic links: implications for Permian global marine biogeography and climate change

SHI GUANG R.; TABOADA ARTURO C

Perth

Congreso; XVII International Congress on the Carboniferous and Permian; 2011

Geological Survey of Western Australia

Strong antitropicality has been noted in the global distribution patterns of Late Palaeozoic biotas, for both animal and plant fossil records. However, just as there has been an extensive debate surrounding the origin of the modern biotic antitropicality, palaeobiogeographers are also deeply divided with regard to the initiation, dynamic development and underlying control mechanisms of this phenomenon in the fossil record. Existing models relevant to antitropicality in ´deep time´ tends to emphasise the role of tectonic vicariance events, surface ocean currents, palaeogeography and suitable climatic conditions in the long-distance dispersal of antitropical taxa. Other alternative models are available but limited. The present study is built on recent new discoveries of well preserved Carboniferous-Permian antitropical brachiopod taxa from Argentina. These new reports not only have confirmed the presence of Late Palaeozoic biotic antitropicality between Gondwana and the Arctic, but have also allowed us to reassess the relative strength of the various existing scenarios invoked to explain the origin and development of this remarkable Late Palaeozoic biogeographical phenomenon. 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 (Viséan) through Verchojania (Moscovian-Kasimovian) to Jakutoproductus (Asselian-Sakmarian), 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 Late Palaeozoic antitropicality remains a viable scenario. If parallel evolution was indeed the mechanism for initiating Late Palaeozoic antitropicality between Argentina and Siberia, it must have commenced during the late Viséan at a time when the Earth was experiencing a global cooling phase allowing the trans-oceanic and global dispersal of some cool-water brachiopod genera from lower to higher latitudes. 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 little understood, although several possibilities could be discussed. Obviously, the role of Antarctica is critical in this discussion due to its position between South America and Australia during the Late Palaeozoic; however, the scarcity of Late Palaeozoic marine fossils found in Antarctica presents a great challenge for any further studies in this regard.