A leaf economics analysis of high-latitude Glossopteris leaves using a technique to estimate leaf mass per area

By the end of the Permian (∼252 Ma), atmospheric CO₂ concentration and temperature had risen sharply as the Earth underwent a time of rapid global warming. The distinctive leaf of glossopterid plants, a group of extinct seed ferns, can be found at southern high paleolatitude localities throughout the Permian. During this time in Antarctica, plants existed in warm environments at polar paleolatitudes where they were subjected to light regimes not experienced by plants today (4 months of continuous light and 4 months of continuous dark). An analysis of the leaf mass per area (LMA) of late Permian Glossopteris leaves from Antarctica gives several insights into how these fossil leaves fit into functional groups and habitats compared to extant plants. The predictive intervals (PI) for Glossopteris LMA (PI: 96.6–129.4 g m⁻²) span the range of LMAs associated with both deciduous and evergreen leaves. When combined with the known effects of high CO₂ and continuous light conditions on leaf LMA, the data suggest that the glossopterids living in these polar latitudes had seasonally deciduous leaves and adaptations that allowed them to thrive in a continuous light environment.