Fossil forests reveal a subtropical Antarctica

Check out my new blog here.

Antarctica today is buried under a sheet of ice up to 5 miles thick, but this wasn’t always the case.  Fossilized forest stands of the now-extinct tree known as Glossopteris have been found in northeastern Antarctica. These trees existed in stands as thick as 20,000 per acre. These fossils have been found at 20-25 degrees from the South Pole; a latitude which today receives no sunlight for half of the year.

Glossopteris fossils provide important evidence for currently accepted distribution of continental plates in the Permian period that ended 250 million years ago. Fossils have been found in regions as distant as Patagonia, India and southern Australia. In the Permian, these landmasses were joined into a southern supercontinent known as Gondwana. The mass extinction that marks the end of the Permian period is believed to have led to the disappearance of Glossopteris.

The distribution of several extinct species in Gondwana. Glossopteris distribution shown in green.

These ancient forests tell more than just continental distribution, however- they provide insight into ancient climates, and possibly even into a major event in plant evolutionary history.

Paleobotanists have reconstructed Glossopteris as a tree that tapers upward like an evergreen. However, the leaves of this tree were broad and lance-shaped, and are thought to have fallen at the end of the growing season. A much warmer climate would have had to exist for such a tree to flourish. This corroborates paleoclimate data, which places Antarctica in a subtropical climate zone during the Permian.

A specimen of Glossopteris with well-preserved reproductive structures was found in Queensland, Australia. Dating to 250 million years ago, the structures found in this specimen indicate a very simple form of pollination . The pollen tubes and ovule examined from this in Glossopteris imply a close relationship with extant seed plants such as conifers and angiosperms. Angiosperms, the widespread group of flowering plants that dominate many terrestrial ecosystems today, are not thought to have evolved until over a hundred million years later. Glossopteris may therefore represent a missing link in the early evolution of pollination biology.

An artist’s rendition of a Glossopteris tree

For anyone interested in the evolutionary history of plants, this is a great interactive timeline developed by plant biologists at Cambridge University.

http://www.ensemble.ac.uk/projects/plantsci/timeline/timeline.php

Citations
1.    Nishida, H., Pigg, K.B. & Rigby, J.F. Palaeobotany: Swimming sperm in an extinct Gondwanan plant. Nature 422, 396-397 (2003).
2.    Pigg, K.B. & McLoughlin, S. Anatomically preserved Glossopteris leaves from the Bowen and Sydney basins, Australia. Review of Palaeobotany and Palynology 97, 339-359 (1997).
3. Peter Jupp on “Ancienct Destructions”
http://www.ancientdestructions.com/site/destructions/antarctic-fossil-forests.php

Advertisements

2 thoughts on “Fossil forests reveal a subtropical Antarctica”

  1. I am impressed! Blog message posted here is quite my friend. I just after to hint keep up with comments and calibre work. IE browser bookmarks to your blog solely in the present climate, I l light on pursuing to regard my friends more in the future! The color of the layout is not rotten, it is elementary on the eyes.

  2. Very nice web page. Thanks for your work and for posting all this. Enjoyed it very much.

    I do have one quibble, which I assume is a mistake.

    “These trees existed in stands as thick as 20,000 per acre. ”

    There are 43,560 sqft per acre. That would give each tree 2 sqft of living space, which is ridiculous. Maybe 2,000 per acre, with each tree having 20 sqft. Even that seems tight, but more realistic.

    Otherwise, thanks.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s