Scientists find tree with leaves 350 million years old – 02/05/2024 – Science

The tree looks like it came out of a science fiction film or a children’s book: a very thin and straight trunk, without branches, topped by a cluster of very long leaves, which could have reached almost 3 m in length. At around 350 million years old, the strangeness of Sanfordia densifolia It is fully justified by the fact that almost no tree from the same period has reached us so preserved.

In fact, the vast majority of the world’s most primitive trees are known only from their roots and trunk parts. The exceptional preservation of specimens of S. densifolia, including much of the detail of the leaves and the top of the plant, documents an important phase in the evolution of Earth’s forests. That’s when these environments began to develop a “ladder” of species, with various height levels and distinct adaptations to deal with varying intensities of light.

The description of the new tree species, whose relationship with other plants of the time is still unclear, has just been published in the specialized journal Current Biology. The fossils were found in the Canadian region of New Brunswick, but the study coordinator, Robert Gastaldo, works in the Department of Geology at Colby College, in the USA.

“The way this tree produced immensely long leaves around its skinny trunk, as well as the enormous number of these leaves on a relatively short trunk, is impressive,” said Gastaldo in an official statement. The researchers estimate that, in life, the plant measured around 3 m tall and had a trunk diameter of 16 cm. The leaves could spread over a diameter of at least 5.5 meters around the tree.

“We all have a mental image of what a tree should be, depending on where we live. The fossil we are presenting is unique and represents the flowering of something strange in the history of life. It is one of the evolutionary experiments that emerged during a time when Forest plants have diversified, and it is a form that appears to have existed for a short time”, analyzes the researcher.

The extraordinary luck in preserving the plant structures is due to the fact that the trees were growing on the edge of a lake when earthquakes severely affected the region. Buried quickly, the plants went through the fossilization process before they began to decompose. In fact, it is no coincidence that they lived during the geological period called Carboniferous: they were transformed, for all intents and purposes, into forms of mineral coal (“Carboniferous” means “coal-bearing”, because of the large reserves of fuel derived from this period).

The formation of the first forests was accompanied by a process of competition between different groups of plants, with each of them trying to find its own space in obtaining sunlight and soil resources.

This led to the formation of the structural complexity that we see in today’s forests, in which some trees are specialized in growing vertically as quickly as possible, forming the so-called canopy of the forest, while others occupy several lower levels, until they reach low-lying plants.

Gastaldo and his colleagues argue that, considering the other fossils from the period and the characteristics of the S. densifolia, it is likely that it is the first tree species known to form the so-called understory, in an intermediate position between the tallest plants and the undergrowth. Its strange leaves were perhaps adapted to capture light in the most efficient way possible in this complex and evolutionarily innovative context.