Analysis of very ancient plant fossils found in South Africa dating from the Lower Devonian allows us to learn more about the transition from barren continents to the green planet we know today. A study in which Cyrille Prestianni, paleobotanist at the EDDy Lab at ULiège, participated, and the results of which have just been published in the journal Scientific Reports .
The greening of the continents – or terrestrialization – is undoubtedly one of the most important processes that our planet has known. While for most of Earth’s history the continents were devoid of macroscopic life, starting in the Ordovician (480 million years ago) green algae have gradually adapted to life outside of the aquatic environment. The conquest of the land emerged by plants was a very long process during which the plants gradually acquired the ability to stand erect, to breathe in the air or to disperse their spores. Plant fossils that document these transitions are very rare. In 2015, during the expansion of the Mpofu Dam (South Africa), researchers discovered numerous plant fossils in geological strata dated to the Lower Devonian (420 – 410 million years ago), making this a truly exceptional discovery.
” Quickly, the discovery turned out to be out of the ordinary ,” explains Cyrille Prestianni, paleobotanist within the EDDy Lab * (Geology / F aculty of Sciences research unit ) at the University of Liège, since we are in the presence of the oldest fossil flora in Africa and that it is very diverse and of exceptional quality ”. It is thanks to a collaboration between the University of Liège, the IRSNB (Royal Institute of Natural Sciences of Belgium) and the New Albany Museum (South Africa) that this incredible discovery was able to be studied. The study just published in the journal Scientific Reports describes this particularly diverse fossil flora with no less than fifteen species analyzed, three of which are new to science. “This flora is also particularly interesting by the quantity of more or less complete specimens which could be discovered there,” continues the researcher. These plants are small in size, with the largest specimens not exceeding 10cm in height. They are simple plants, made up of axes that divide two to three times and end in reproductive structures called sporangia. ”
The fossil flora of Mpofu, allows us today to imagine what the world could look like when the largest plants did not exceed the height of our ankles and that almost no animal had yet been able to free itself from the aquatic environment. . It allows us to better understand how our Earth went from a red boulder devoid of life to the green planet we know today. These plants, as simple as they are, are a crucial step in building the environments that welcomed the first arthropods. They are the basis of the long history of life on Earth, which continues today from dense tropical forests to arid tundra in the north.
* The Evolution and Diversity Dynamics Lab (EDDy Lab) of the University of Liège is the heir to a long paleontological tradition, particularly in the study of Terrestrialization processes. The work presented here is the result of a long collaboration between ULiège and IRSNB, which are the two French-speaking Belgian institutions that are leaders in the field of paleontological sciences.
Featured image: Uskiella spargen a small plant whose axes divide several times before bearing oval sporangia. Credit: Cyrille Prestianni
Robert W. Gess & Cyrille Prestianni, An Early Devonian Flora from the Baviaanskloof Formation (Table Mountain Group) of South Africa , Scientific Reports , June 2021.
Provided by Liege University