Early Permian sphenophyllales from Patagonia, a reappraisal

CÚNEO, RUBÉN; ESCAPA, IGNACIO; TOMESCU, MIHAI

Edmonton

Congreso; BOTANY 2015; 2015

The fossil record of sphenophyllales shows a significant disparity in stratigraphic ranges between Euramerica and Gondwana. Whereas in Euramerica the group played an important role in wetland plant communities during the Pennsylvanian, subsequently losing much of its prominence at the beginning of the Permian, in Gondwana sphenophyllaleans only became remarkably abundant in the Permian, as demonstrated by the Patagonian fossil record. Given the climatic sensitivity of this plant group, it is likely that in both cases its geographic distribution was affected by the global-scale climatic shifts that occurred at the end of the Pennsylvanian and beginning of the Permian. These shifts involved transition from ice-house to green-house conditions and from wetland to dryland ecosystems in most of the northern hemisphere, and a transition in the opposite direction in the southern continents. We discuss the close similarities in vegetative and reproductive features between Patagonian and Euramerican sphenophyllales, and propose an allopatric speciation model according to which the group originated in the northern hemisphere and radiated southwards starting in the latest Pennsylvanian. While the paleogeographic details of this model have yet to be refined, we propose that Patagonia represented an early dispersal direction of this radiation, in the Early Permian: its geography and climate, similar to those of Euramerica, favored the diversification of sphenophyllales, as well as other plant groups, such as lycophytes and ferns, which may have followed similar radiation patterns. It is likely that Patagonia acted as a new center from which these groups subsequently radiated to reach most of the other Gondwanan subcontinents during the Permian.