Before the first mammals, before dinosaurs roamed the earth, a plant grew in Gondwana, a large continent in the Southern Hemisphere.
Nearly 280 million years later, in what is now Brazil, scientists have identified the fossil remains of the plant as an early member of a genus called cycads, or cycadales, which continues to this day. The discovery increases the scientific understanding of the resilience of these plants, which continued through two mass extinctions.
“The vegetative anatomy of this plant is strikingly similar to that of today,” said Rafael Spiekermann, a graduate student at the Senckenberg Research Institute and Natural History Museum in Germany and the lead author of a paper describing the fossil in the journal Review of Palaeobotany and Palynology.
The species that was preserved was named Iratinia australis; ‘Australis’ is Latin for ‘south’, and the fossil comes from the southern part of a rock layer known as the Irati Formation. It is a small piece of wood – a little over five inches long, about 2.5 inches in diameter – but it was enough to see that it shared the most important features with plants that live today.
“If you cut a cycadale with a machete today,” he said. Spiekermann said, “you will see the same anatomical pattern that you can see in our fossil.”
The surviving cicadas are often called ‘living fossils’, much like modern-day coelacanth fish, which retain many of the same characteristics as ancestral fish hundreds of millions of years ago.
This generation endured some catastrophe when most of the planet’s lives were killed. The first occurred 250 million years ago at the end of the Permian geological period and is often called the Great Dying. It was the largest mass extinction in Earth’s history, opening the evolutionary door to the rise of dinosaurs. The other was the extinction of 66 million years ago that brought the dinosaur era to an end.
“It’s a very long history on earth,” said André Jasper, a professor of biology at the University of Taquari Valley in Brazil, and an author of the article. ‘You can find it, this kind of plant, in Australia, Asia, Africa, America. It spread all over the world. ”
Cycadales never dominated the plant kingdom, although they thrived in certain places. Their flowering period was more than 120 million years ago before they, and even older plants such as conifers, were overwhelmed by the advent of flowering plants, which reproduce faster and adapt to changing ecological niches.
“These guys were dinosaur food,” says Dennis Stevenson, an emeritus senior curator at the New York Botanical Garden and an expert on cycadales who was not involved in the research.
Cycadales, however, never disappeared, and there are about 350 species today. The best known is perhaps the Sago palm, an ornamental plant that looks like a small palm tree but is not actually a palm tree.
Rather, like all cicadas, a sago palm has a distinctive structure of veins running from its leaves through its stem. The fossil cicadals also retain this feature, called girdle leaf spores.
The Iratinia australis fossil was excavated several decades ago. Based on its leaf shapes, botanists have misidentified it as part of another group of plants known as lycopsids. Lycopsids were numerous in this part of Gondwana at the time, so the fossil did not get much attention until Mr. Spiekermann, who is working on his doctoral dissertation on lycopsids, did not take a closer look.
“I saw a very different anatomy,” he said. Spiekermann said.
Some petrified leaves of the same era, which are thought to be parts of cicadal plants, were previously found in China. But that was the first look at the woody part of an old cycadale.
“The anatomical details are just amazing,” said Dr. Stevenson said. “I think this is what every paleobotanist dreams of finding – and the first one identified in the rocks of earlier Gondwana.”
The widespread geographical distribution indicates that even then cycadales existed for some time.
“The idea is: Wow, we have one of those kinds of things here in Brazil and the other in China,” said Dr. Stevenson said. “The guys have to be a lot older than we have so far in the fossil record to get all over the earth.”
William A. DiMichele, curator of paleobotany at the Smithsonian National Museum of Natural History, who was not involved in Iratinia australis research, said the discovery was part of the trend of ancient plants becoming even older.
“There have been many discoveries in the last, for example, 10 to 15 years of plants appearing significantly earlier than previously thought to exist,” he said.