The 366 daily episodes in 2014 were chronological snapshots of earth history, beginning with the Precambrian in January and on to the Cenozoic in December. You can find them all in the index in the right sidebar. In 2015, the daily episodes for each month were assembled into monthly packages, and a few new episodes were posted. Now, the blog/podcast is on an occasional schedule with diverse topics, and the Facebook Page showcases photos on Mineral Monday and Fossil Friday. Thanks for your interest!

Friday, August 8, 2014

August 8. Glossopteris



Glossopteris leaves

One of the first lines of evidence leading to the acceptance of continental drift was a shrub called glossopteris. It was a seed fern that lived during Permian time (with some questionable successors in the Triassic). They were among the dominant plants of the Permian, and contributed significantly to the Permian coal beds that are important reserves today in South America, South Africa, India, Australia, and even Antarctica, where they were collected by Robert Scott’s expedition. That’s right, despite the episode titled “The End of Coal” last month, plants did continue to make coal under the right circumstances.  

Glossopteris seeds were large – too large to be distributed by the wind. That observation and the presence of glossopteris across the southern continents that are now widely separated led Austrian geologist Eduard Suess to suggest that the southern continents had once been attached, either via land bridges or in a single supercontinent, Gondwana. It wasn’t much of a leap to connect Gondwana with the other continents in Pangaea, although it was tectonic and stratigraphic evidence that led to that, rather than glossopteris. Some glossopteris-like fossils have been found in the northern continents, but I think the general consensus is that it was restricted to the southern continent of Gondwana.

Glossopteris distribution (dark green) across Gondwana
The plant was a shrub or tree, with some as tall as 100 feet. The name means “tongue-leaf” for the simple lobate shape of the leaves.

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Benjamin Silliman was born August 8, 1779, in New Stratford, Connecticut. He was a professor of chemistry and geology at Yale, where he built up the mineralogy collection that formed the core of the Yale Peabody Museum. He was one of America’s first real science professors, and he established the American Journal of Science, the oldest scientific journal in the U.S.
—Richard I. Gibson

Photo by Daderot (public domain) 

Glossopteris distribution map by Petter Bøckman (public domain, via Wikipedia) 

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