Rare 3D fossils show some early trees had shapes unlike any you’ve ever seen

In the fossil record, trees are usually preserved with only their trunks. They generally do not include sheets to show what their canopies and general shapes may have looked like. But now the researchers report in the journal Current biology describe fossilized trees from New Brunswick, Canada, with a surprising and unique three-dimensional crown shape.

“The way this tree produced extremely long leaves around its spindly trunk, and their number over a short length of trunk, is surprising,” says Robert Gastaldo of Colby College in Waterville, Maine.

The shapes taken by these 350 million-year-old trees resemble those of a fern or a palm tree, even though palm trees did not appear until 300 million years later, he explains. However, the functional leaves of ferns or palms cluster at the top and are relatively few in number.

“In contrast, Sanfordiacaulis retains more than 250 leaves around its trunk, with each partially preserved leaf extending 1.75 meters,” says Gastaldo.

“We estimate that each leaf grew at least another meter before it ended. This means that the ‘bottle brush’ had a dense canopy of leaves that extended at least 5.5 meters (or 18 feet) around of a non-woody trunk and only 16”. centimeters (or 0.5 feet) in diameter. Surprising to say the least.

This work was made possible through a long-term international collaboration with Matthew Stimson and Olivia King of the New Brunswick Museum, Saint John, and Saint Mary’s University in Halifax.

The researchers’ findings offer important insights into the evolution of plants and trees, that is, plants that reach the height of a tree, or at least 15 feet, at maturity. They also serve as a reminder that throughout the history of life on Earth, there have been trees unlike any we’ve ever seen before, some of which appear to have come from the imagination of Dr. Seuss, the researchers say. .

“We all have a mental idea of ​​what a tree looks like, depending on where we live on the planet, and we have a vision of what is familiar to us,” says Gastaldo. “The fossil we are talking about is unique and represents a strange growth form in the history of life. It is one of the experiments of evolution at a time when forest plants were undergoing biodiversification, and it is a form that appears to have a short lifespan.”

The fossils in question were preserved by the catastrophic burial of trees and other vegetation caused by an earthquake along the edge of a rift lake. The first fossil tree was discovered about seven years ago in a quarry, but it included only a partial sample. It took several years to also find four other specimens of the same plant, in spatial proximity, explains Gastaldo.

One of the specimens revealed how the leaves spread away from the top of the tree, making it “absolutely unique”. According to the researchers, it is one of the rare fossil specimens dating back more than 400 million years to preserve a trunk around which the crown leaves are still attached.

“Any fossil tree with an intact crown is a rarity in the history of life,” says Gastaldo. “The fact that the crown leaves are attached to a trunk, in itself, raises the question of what type of plant this is, how is this plant organized, and is it a form that continues to the present, or is it outside the “normal” concept of a tree? All these questions, and many more, led to this multi-year effort.

Researchers report that the tree likely relied on its unusual growth form to maximize the amount of light it could capture and reduce its competition with other plants on the ground. They suggest the tree now represents the first evidence of smaller trees growing beneath a taller forest canopy.

This means that plant life in the early Carboniferous was more complex than expected, suggesting that Sanfordiacaulis lived at a time when plants were “experimenting” with a variety of possible shapes or architectures.

“The history of life on earth is made up of plants and animals that are unlike any living today,” says Gastaldo.

“Evolutionary mechanisms operating in the deep past gave rise to organisms that lived successfully for long periods of time, but their shapes, growth architectures, and life cycles followed different trajectories and strategies. Rare fossils and unusual ones, like the New Brunswick tree, is just one example of what colonized our planet but proved to be an unsuccessful experiment.”