Karoo insects, plants tell ancient tale
A SMALL, unassuming road-cutting is producing thousands of exquisitely preserved fossils in the Sutherland District of the Northern Cape.
In research recently published in the Nature journal, experts from the Albany Museum in Makhanda, Rhodes University, Evolutionary Studies Institute at Wits University, UCT and the Stuttgart State Museum of Natural History in Germany, among others, explain how these tiny fossils of plants and insects, many of them only millimetres long, reveal a previously unknown ecosystem on the quiet shores of a pool 266 million years ago.
The authors, in a statement by GENUS, a collective knowledge hub and an inclusive network for Palaeosciences in Africa at Wits University, said plants, insects and small things tend not to share the limelight with dinosaur and hominid discoveries, but the stories they tell can be just as fascinating and their message powerful.
“We currently know a fair bit about the reptilian animals that roamed the Karoo of South Africa during the middle Permian Period, a time long before the dinosaurs appeared. These creatures included the predecessors of tortoises and the strange and lumbering therapsids that would later give rise to the mammals, but we have little idea about what else was around at the time,” the authors said.
They are now gaining a better understanding of what the world looked like before the onset of two key extinction events in Earth’s history, at the end of the Guadalupian Epoch (~260 million years ago) and then the largest extinction event ever, at the end of the Permian Period (~252 million years ago).
“Our new fossils will change ideas about the evolution of some important plant and insect groups and their distributions across the ancient supercontinent of Pangaea.
“The superb quality of fossil preservation means that soft-bodied organisms that very rarely preserve in the fossil record are present at the site.”
For example, the oldest freshwater leech in the world pushes the fossil record of the group back by 40 million years. Even more extraordinary are the water mites that are 150 million years older than previously known.
A new, early damsel-fly and hundreds of tiny nymphs belonging to the stoneflies, a group that still lives in streams today, are the oldest records from Gondwana.
Early relatives of the cicadas, the strange, extinct Palaeodictyoptera and many sap-sucking bugs (Hemiptera) are just some of the other insect discoveries.
The plants found at the site are mostly Glossopteris leaves. Great forests of these trees formed most of the economically important coal reserves in South America, Australia, India,
Antarctica, Madagascar, and southern Africa. Aside from its economic importance, Glossopteris is a botanically weird plant. Scientists have been debating where it fits within the Plant Kingdom for nearly 200 years.
Text-books detail that it is a seedfern, but the new fossils prove that it produced cones, and is in fact a conifer, the same group of plants that includes the yellowwoods and pine trees that grow today.
The authors said their excavations are continuing and they are still finding new kinds of fossils every field season. “We are also working hard to describe each of the beautiful plants and creatures that have emerged and are trying to figure out why fossils were preserved so beautifully in this area.”