Antarctic Wood Transantarctic Mountains, Antarctica

In the Middle Triassic, Antarctica was the heart of the supercontinent Gondwana, joined to Africa, India, South America, and Australia. It sat at a high polar latitude of roughly 70 to 75 degrees south, not far from where it is now. The difference was the climate.

The Triassic was a greenhouse world with no polar ice caps. Cool, humid conditions allowed forests to grow along rivers and floodplains well inside the polar circle. Nothing like them exists anywhere on Earth today.

At that latitude, the trees had continuous daylight through the summer and total darkness through the winter. The fossil wood records how they coped. Its growth rings show fast growth during the light season, then an abrupt stop as winter arrived.

Thick mats of fossil leaves found around the stumps suggest the trees were deciduous. They likely dropped their foliage and went dormant through the polar night, a survival strategy with no exact modern equivalent.

The Fremouw forests were dominated by corystosperms, a group of extinct seed ferns that grew as true trees. Their forked leaves, called Dicroidium, are the most characteristic plant fossil of the Southern Hemisphere during the Triassic.

Corystosperm wood from the Fremouw Formation was named Kykloxylon fremouwensis in 1993. Later research assigned large, anatomically preserved trunks from Fremouw Peak to the same genus. Corystosperms disappeared by the end of the Triassic and left no living descendants.

A definitive genus- or species-level identification of fossil wood requires microscopic thin sections. These show the growth rings, cell-wall pitting, and ray structure that separate one wood type from another.

This specimen has been kept intact rather than cut for sectioning. Its attribution is therefore based on its locality, its visible woody structure, and the known composition of the Fremouw flora, where corystosperm wood predominates. "Possible" is the scientifically best way to state it.

The Fremouw Formation is also famous for its vertebrate fossils. In 1969, the lower, slightly older part of the formation yielded bones of Lystrosaurus, a stocky, plant-eating mammal relative already known from South Africa and India.

Finding the same animal on the frozen continent was a landmark moment. It strongly supported the idea that the southern continents were once joined as Gondwana, helping confirm continental drift and plate tectonics.

Trees and branches were buried by river sediment. Mineral-rich groundwater then seeped through the buried wood, depositing minerals within and around the plant cells. This permineralization preserved the wood's original structure.

In this specimen, some of the original carbon survived alongside the minerals. It is a partial window into the living tree. Elsewhere in the formation, silicified peat preserves plant tissue so finely that roots, spores, and even fungi can be studied under the microscope.