Progymnospermopsida is a class of woody plants that existed for a short time during the Mid to Late Devonian. The group is characterized by having wood anatomy like gymnosperms (cone-bearing seed plants), but lacking seeds, and rather reproducing rather by spore dispersal, like ferns (1, 2). This group represents an important evolutionary transition, having given rise to seed plants. The most iconic progymnosperm is Archaeopteris, which had a worldwide distribution in the Late Devonian, totally dominating forest ecosystems. Archaeopteris was a gigantic tree, the largest to have existed on Earth by that time. Archaeopteris trees were larger, longer lived, and had deeper root systems than earlier plants, allowing them to pioneer new habitats. Archaeopteris forests may have played an important role in Late Devonian climate change and biotic crises (3) as forestation changed weathering rates on land and led to massive carbon drawdown from the atmosphere.
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Archaeopteris notosaria
Localities: Waterloo Farm and Coombs Hill
Age: Famennian
Archaeopteris notosaria is the oldest known type of woody tree from southern Africa. It was diagnosed from the Waterloo locality (4). Until research began at the Waterloo site it was not known that Archaeopteris forests had extended so far from the equator. Previous discoveries of Archaeopteris all come from strata that were deposited in tropical to subtropical climates, whereas the Waterloo Farm lagerstätte was situated at high latitude (4).
New material of the species from Coombs Hill contributes only its second known occurrence. This includes remarkably intact remains including complete frond-like 'lateral branch systems'. This was the deciduous unit of the plant, which was dropped seasonally. Additionally, fertile 'proto-cones' of the plant at Coombs Hill allow us a much more detailed understanding of the reproductive structures of the species (unpublished result).
The appearance of Archaeopteris in the southerly latitudes of Gondwana marks the earliest evidence for the truly global extent that forests reached by the Late Devonian. There is much more to be learned about the earliest high palaeolatitude forests, such as, for instance, the size attained by the trees and their species composition.
Localities: Waterloo Farm and Coombs Hill
Age: Famennian
Archaeopteris notosaria is the oldest known type of woody tree from southern Africa. It was diagnosed from the Waterloo locality (4). Until research began at the Waterloo site it was not known that Archaeopteris forests had extended so far from the equator. Previous discoveries of Archaeopteris all come from strata that were deposited in tropical to subtropical climates, whereas the Waterloo Farm lagerstätte was situated at high latitude (4).
New material of the species from Coombs Hill contributes only its second known occurrence. This includes remarkably intact remains including complete frond-like 'lateral branch systems'. This was the deciduous unit of the plant, which was dropped seasonally. Additionally, fertile 'proto-cones' of the plant at Coombs Hill allow us a much more detailed understanding of the reproductive structures of the species (unpublished result).
The appearance of Archaeopteris in the southerly latitudes of Gondwana marks the earliest evidence for the truly global extent that forests reached by the Late Devonian. There is much more to be learned about the earliest high palaeolatitude forests, such as, for instance, the size attained by the trees and their species composition.
References:
1) Taylor T. N., Taylor E. L., Krings M., (2009). Paleobotany: The biology and evolution of fossil
plants. Elsevier
2) Meyer-Berthaud, B., Scheckler, S. E., & Wendt, J. (1999). Archaeopteris is the earliest known modern tree. Nature, 398(6729), 700.
3) Algeo, T. J., & Scheckler, S. E. (1998). Terrestrial-marine teleconnections in the Devonian: links between the evolution of land plants, weathering processes, and marine anoxic events. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences, 353(1365), 113-130.
4) Anderson, H. M., Hiller, N., & Gess, R. W. (1995). Archaeopteris (Progymnospermopsida) from the Devonian of southern Africa. Botanical Journal of the Linnean Society, 117(4), 305-320.
1) Taylor T. N., Taylor E. L., Krings M., (2009). Paleobotany: The biology and evolution of fossil
plants. Elsevier
2) Meyer-Berthaud, B., Scheckler, S. E., & Wendt, J. (1999). Archaeopteris is the earliest known modern tree. Nature, 398(6729), 700.
3) Algeo, T. J., & Scheckler, S. E. (1998). Terrestrial-marine teleconnections in the Devonian: links between the evolution of land plants, weathering processes, and marine anoxic events. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences, 353(1365), 113-130.
4) Anderson, H. M., Hiller, N., & Gess, R. W. (1995). Archaeopteris (Progymnospermopsida) from the Devonian of southern Africa. Botanical Journal of the Linnean Society, 117(4), 305-320.