Forests of giant, scaly-stemmed mosses emerged from ancient swamps in Atlantic Canada 350 million years ago.
But beneath the canopy grew even stranger trees, fossils of which were recently discovered in a quarry in Norton, New Brunswick.
“What it really looks like is one of those truffle trees from The Lorax” said Olivia King, one of the researchers who discovered the fossil. She referenced a famous children’s picture book by Dr. Seuss that features fantastical, colorful trees being decimated to produce clothing called “thneeds.”
Like the truffle, the new fossil species, Sanfordiacaulis densifolia, was a little larger than a human, but not extremely tall (around three meters), and had a spindly stem that nestled in a dense mop of long leaves. This mop had a more extreme size than that of the truffle: more than five meters, or approximately the diameter of an above-ground swimming pool.
“It’s unlike anything we see today,” said Matthew Stimson, who co-discovered the fossil, described in a new study published in Current Biology Friday.
How it was found in a quarry in New Brunswick
Sanfordiacaulis lived in an era called the Mississippian, an early part of the Carboniferous period. This was before the evolution of dinosaurs or even reptiles, and salamander-like insects and amphibians were just beginning to colonize the earth. At the time, New Brunswick had a subtropical to tropical climate and its lakes were surrounded by swamp forests.
Both King and Stimson are graduate students at St. Mary’s University in Halifax and also work for the New Brunswick Museum. They looked for traces of these early animals, often in quarries that allowed it, because these are places where fresh rock is constantly exposed while digging.
At Sandford Quarry, the sandstone comes from the bottom of a very long, ancient lake so deep that near its bottom there was no oxygen to aid decomposition. It has preserved not only the fish, but also sections of the surrounding forest plunged into its depths by earthquake-triggered landslides.
While searching there in 2017, King and Stimson spotted a tree trunk embedded in a rock. As they dug it up to uncover more, they realized that the trunk was attached to branches and leaves that didn’t belong to anything they recognized.
“It was something new, something unique,” Stimson said.
They began sending photos to fossil plant experts to help them identify it.
They also contacted the quarry owner, Laurie Sanford, who offered her staff and machinery to extract the rock and transport it to the New Brunswick Museum. The fossil is named for his contributions.
What this tells us about the history of trees
Robert Gastaldo, professor emeritus at Colby College in Waterville, Maine, was among the paleobotanists called in to help identify and study this unusual plant. He remembers walking into the room where the huge block was stored, with the tree embedded inside. “And (I) said, ‘Oh wow.'”
Not only was it large, but it is very unusual to find the crown of a tree preserved with a trunk, he said. It is also unusual that they are preserved in three dimensions, instead of being flattened during the fossilization process.
Study co-author Adrian Park, a geologist with the New Brunswick Department of Natural Resources and Energy Development, found evidence of earthquake-triggered landslides at the fossil site. Researchers believe that sediment that enveloped the tree during an ancient landslide protected it from being crushed by additional sediment accumulating above over the hundreds of millions of years that followed .
Gastaldo said very large lily trees and low understory plants had previously been found in Mississippian forests, but researchers had not yet found evidence of a middle layer of intermediate-sized trees , like those in the “undercover” of modern tropical forests – until this one.
Its immense clump of dense foliage was probably intended to capture as much light as possible between the canopy and the undergrowth.
Gastaldo said the existence of such a strange tree suggests it was a time when plants, which had only recently colonized the land, were experimenting with many different shapes and strategies.
King noted that in the case of the form taken by Sanfordiacaulis, “we don’t see it before this time and we don’t see it after. So it’s a bit of a failed experience. »
That said, Sandfordiacaulis had short-lived success – further digging led researchers to find four more specimens, and it turned out that many of its leaves and branches had previously been collected, but not identified, suggesting that it was was a fairly common plant in its forest.
The most similar modern plants, tree ferns and palms, have far fewer leaves and evolved only later.
What this tells us about old-growth forests
Plant fossil researchers who were not involved in the study were excited about the implications for what forests were like 350 million years ago.
Cindy Looy is a professor at the University of California, Berkeley, who teaches paleobotany and studies how ancient plants responded to major environmental changes, such as mass extinctions and deglaciations. She said she was struck by the image of what the tree would have looked like.
“This plant should have looked almost like a gigantic umbrella if you had been standing under it. Almost no light could escape this plant,” she said. “It’s an unusual model and pretty cool.”
Will Matthaeus is a postdoctoral researcher at Trinity College Dublin who measures and integrates fossil plants into simulations of ancient ecosystems.
He said that while plants this old are usually strange-looking, “this is the top of the heap in terms of an unfamiliar-looking tree.”
“It sounds a bit like something out of a Dr. Seuss book, I think,” he said, not knowing that the study authors had come to the same conclusion.
Looy and Matthaeus said finding an entire tree with a trunk, branches and leaves was very rare. But they were very excited that this tree provided the first evidence that forests were complex enough to have a middle layer of plants, even 350 million years ago, between the canopy and the understory.
“They’re looking back at a time when we don’t really know what the forest ecosystem looked like,” Matthaeus said. “Findings like this are revolutionary in that sense.”
The new study was supported by scientific and research funding from the Canadian, US and UK governments as well as the New Brunswick Department of Natural Resources and Energy Development.