We had a discussion about the origins and classification of the Glossopteridales. The debate was whether they belonged to the Gymnosperm group or to the Pteridosperm group of plants. The web sites below show that there is a difference of opinion. You will find more references to their Pteridosperm affinities (based on the fern-like sporophyte structures on the leaves) than to their Gymnosperm affinities (based on broader characterisitcs such as overall form and structure of the bole (trunk). The distinction is beyond the level of the class, but does serve to illustrate the confusion that can arise with fossil plants of uncertain origin and with characteristics that do not fit neatly within existing classification schemes.
Long considered a fern after its discovery in 1824, it was later assigned to the gymnosperms. It is regarded by some authorities as being close to the ancestral angiosperm, or flowering plant. Certain poorly preserved reproductive structures associated with the leaves may in fact be the seed-bearing capsules of Glossopteris. Glossopteris is the key plant in a fossil assemblage called the Glossopteris flora, which also includes several related fossil genera (e.g., Lidgettonia and Gangamopteris) in Late Paleozoic rocks of South Africa, India, Australia, and South America.
Long considered a fern after its discovery in 1824, it was later assigned to the gymnosperms. The genus is placed in the division Pteridospermatophyta. In reality, many of the plant groups included within this division are only distantly related to one another.
The reproductive structures of glossopterids are as unusual as the foliage leaves. They appear to have been borne on leaves as in other “pteridosperms“. Poor preservation has led to much controversy over their structure and their arrangement on living plants from which they came. At least one point has become clear: pollen and seeds were produced in different organs, attached to separate leaves, though the specifics of the organs themselves are not as clearly settled. Pollen organs have been described as anything from a modified leaf bearing stalked pollen sacs to cone-like clusters.
This controversy serves as a great example of the challenges of trying to recreate the past with only a few clues of what it looked like. We saw with the fossils from last week that certain parts of the same fossil can have different names because they were discovered by different people, but still be part of one single organism. Without having an organism intact, reconstruction seems like a guessing game as the Glossopteridales seem to show. Thanks, this was interesting to read about.