The mass extinction at the Permian-Triassic boundary produced a floral turnover in Gondwana in which
Paleozoic seed ferns belonging to the Glossopteridales were replaced by corystosperm seed ferns and other seed plant
groups in the Mesozoic. Secondary growth (wood production) in both plant groups provides information on plant
growth in relation to environment in the form of permineralized tree rings. Techniques utilized to analyze extant wood
can be used on fossil specimens to better understand the climate from both of these periods. Late Permian and early
Middle Triassic tree rings from the Beardmore Glacier area indicate an environment where extensive plant growth
occurred at polar latitudes (~80–85°S, Permian; ~75°S, Triassic). A rapid transition to dormancy in both the Permian
and Triassic woods suggests a strong influence of the annual light/dark cycle within the Antarctic Circle on ring
production. Latewood production in each ring was most likely triggered by the movement of the already low-angled sun
below the horizon. The plants which produced the wood have been reconstructed as seasonally deciduous, based on
structural and sedimentologic evidence. Although the Late Permian climate has been reconstructed as cold temperate
and the Middle Triassic as a greenhouse, these differences are not reflected in tree ring anatomy or wood production in
these plant fossils from the central Transantarctic Mountains.
