Brandy Bay and unique fossil wood from the James Ross Island in Antarctica

Fossil wood is certainly not a ground-breaking or exciting discovery in most people’s eyes. However, the internal structure of the described finding exhibits a unique structure with features corresponding to several gymnosperm groups, including extinct ones. Because of this, this wood could not be included in the well-known genera. Without a specified order, the researchers were forced to create an entirely new genus, Mixoxylon Chernomorets & Sakala.

The internal structure of the wood is exceptional

The specificity of wood lies in multiple properties. The sample, like common conifers, has a more robust zone of earlywood than latewood; however, compared with known related types, such as the otherwise highly similar genus Sahnioxylon, this wood has the opposite character.

The appearance of the wood was probably caused by changes in total precipitation during the year. This tree grew in high latitudes, approximately in the areas where its fossil record comes from (today this is about 64°S, almost by the Antarctic Circle) and certainly played an important role. Mixoxylon was thus exposed to a six-month long and relatively warm polar night when darkness prevailed.

Under these conditions, only limited photosynthesis can take place. However, the tree still had to breathe (transpire) as it did in the polar day to survive. Therefore, the character of wood is probably the result of both the evolutionary development of the genus and these external processes. However, we cannot be certain about this, as there exists no similar tree and environment growing today (Antarctica is now much colder).

Look into the internal morphology

The type, appearance, and position of individual tracheids are unique. Tracheids are an older and less perfect type of vascular system in plants. They occur in some spore plants, are typical of gymnosperms, and, together with vessel elements, are also present in angiosperms. Their function is to transport water and also to strengthen the plant.

Internal structure of the unique wood. Arrows point to scalariforming points. Authors: Chernomorets, O., Sakala, J.

An essential feature of Mixoxylon is the scalariform to araucarian pitting on the tracheids (Fig. 1). Only a few genera of petrified wood exhibit this trait. Nevertheless, it is undoubtedly a seed plant, perhaps an extinct conifer or a derived seed fern. However, the exact classification of the newly found tree in the plant taxonomical system remains uncertain.

The newly defined species Mixoxylon australe Chernomorets & Sakala is known only from the Lewis Hill member of the Whiskey Bay Formation from the Albian (final stage of the Lower Cretaceous, 113.0 ± 1.0 to 100.5 ± 0.9 million years ago). The species name recalls the southernmost known occurrence of a similar type of wood (australis = direction to the south).

Mendel’s Polar Station (Czech Republic)

The Czech Mendel’s Polar Station is located on James Rose Island. It is currently (2022) operated by the Ministry of Education, Youth and Sports together with Masaryk University in Brno. Its construction began in 2004 and it was inaugurated 3 years later. Its founder, geographer and polar explorer Pavel Prošek, was apparently lucky in choosing its location. Near the station, there are paleontologically interesting source rocks, and in addition, the “likable” names of Brandy and Whiskey Bays stand out in scientific articles and on the labels of the fossils found.

Fossil wood source area map. The black star is the exact location of the discovery.  https://bit.ly/3KBiQaQ

Some paleontological finds from the Antarctic Project, including petrified trees, can be viewed in person every Wednesday at our Chlupáč Museum of the Earth History at Albertov 6. All Charles University students have free admission to the museum.

This article received approval from both authors, who attached factual remarks and comments. They deserve a huge thank you for this. They have moved the text one step further towards comprehensibility of the topics discussed.

Chernomorets, O., & Sakala, J. (2021). Mixoxylon australe gen. et sp. nov., a unique homoxylous wood with non-angiosperm affinity from the Lower Cretaceous of Antarctica (Albian, James Ross Island). Antarctic Science, 33(5), 493-501. doi:10.1017/S0954102021000389

Available via ResearchGate.

Jan Geist