Rare Fossils Reveal ‘Absolutely Unique’ Tree From 350 Million Years Ago

A set of rare fossils has revealed a previously unknown and “absolutely unique” type of tree that was present on Earth around 350 million years ago.

These prehistoric trees represent not only a new species but also an entirely new genus, or group of species, according to a study describing the fossils that has been published in the journal Current Biology.

But the authors do not have sufficient evidence to determine whether these trees are part of the fern family, the seed plant family or some other unknown and un-described plant family in the planet’s history.

“The trees are unique to science,” palaeontologist Robert Gastaldo, an author of the study who is with Colby College in Waterville, Maine, told Newsweek.

“Our find is similar to reports from remote regions on the planet today, either on land or in the deep ocean, where scientists ‘find’ a completely new animal or plant never seen before,” he said.

To the general public, the tree, named Sanfordiacaulis densifolia, would likely have looked like a very large and oversized “bottle brush,” Gastaldo said.

To put this in perspective, the growth form of the plant is, in some ways, similar to but very different from two tree forms found in today’s tropics. These tree forms are found in a small number of tree ferns, seed plants and flowering plants.

But these modern trees have leaves arranged in the crown (the top of the tree) that are small in number. Tree ferns, for example, may have 15 to 20 leaves in their crown, and palm trees have a similar number of leaves. When one or more leaves stop photosynthesizing, they either fall off the trunk (leaving a scar where they were attached) or fall against the trunk in what is called a skirt.

By contrast, Gastaldo said, “our plant had more than 250 leaves crowded around a non-woody, 6-inch diameter trunk, and these occur over a trunk length of only 30 inches. On top of this, each leaf likely grew to nearly 10 feet away from the trunk, forming a canopy that was about 20 feet in diameter. Indeed, a very strange organization and growth pattern.”

These plants lived during the Late Paleozoic era, which stretched from around 419 million to 252 million years ago. This latter half of the Paleozoic is divided into the Devonian, Carboniferous and Permian periods. The first trees on Earth are thought to have appeared during the Devonian period (around 419 million to 359 million years ago), whereas the newly described plant dates back to the Carboniferous (around 359 million to 299 million years ago)—specifically, the earliest part of the latter period.

“The time period in which our plant flourished saw a profound and significant diversification of trees in many different plant groups,” Gastaldo said.

He went on: “Plant fossils are rare in Earth’s history. It is even rarer to find a tree fossil with its three-dimensional crown leaves intact. We can count the number of fossil-plant occurrences in the Late Paleozoic on one hand, where tree trunks are preserved with crown leaves attached. And the little tree we found is only one of a small handful of fossil trees where their leaves are still attached to the trunk.”

He continued: “Our fossil is unique evidence of an extreme form of evolution that someone might imagine in their dreams. But, in reality, this exotic tree was part of an ancient landscape that doesn’t exist today nor has existed for the past 350 million years.”

The new species was described based on five different trees discovered close proximity to one another over the past seven years during excavations at the Sanford Quarry in New Brunswick, Canada.

The fossils in question represent trees that once stood along the margin of a rift lake that formed far from the ancient coastline. At the time, the climate in the area would have been subtropical to tropical.

The region would have also experienced earthquakes. The researchers believe these seismic events stripped the trees from the lake margin and caused them to float into the lake before they sank to the bottom, where they were buried and preserved. The chances of the plants being preserved as they were in this way is “exceedingly low,” according to Gastaldo.

“Considering the probability of this happening over the past 350 million years, it is more likely that someone would win the lottery than a tree become fossilized in the manner of ours,” he said.

The interval of time during which the plants from New Brunswick thrived appears to be a transitional period in the evolution of the plant kingdom and trees, according to Gastaldo. In particular, these plants presage forms that became well established during the subsequent Pennsylvanian subperiod—the second major interval of the Carboniferous, which stretched from around 323 million to 299 million years ago.

“I’ve likened our discovery to children’s book illustrators, think Dr. Seuss, or CGI artists—plants in Avatar, for example—who have a weird sense of humor about plant growth architectures,” Gastaldo said.

“The evolution of the plant kingdom underwent many different experimental forms that were successful for some million or more years of time but didn’t survive the test of time for whatever reason,” he said.

Paul Kenrick, a researcher with London’s Natural History Museumwho was not involved in the study, told Newsweek the findings were “significant” because they inform us about the forest structure 350 million years ago. They indicate that in addition to large trees that formed the canopy there was a sub-canopy level of smaller trees.

“During the Devonian period, about 350 million years ago, plants became large, evolving tree-like growth for the first time, which led to the development of forests,” he said. “This change had an enormous consequence for animal life and for physical aspects of our planet, like the chemistry of the atmosphere, global temperature and the water cycle.”

Kenrick said that a key question is to what extent these early forests resembled modern ones.

“This study focuses on a new site from the earliest part of the Carboniferous period, about 359 to 347 million years ago,” he said. “It’s exciting because the fossilized remains of the trees found here are relatively intact, showing their overall growth habit, which is very rare. Fossils like this can be exceptionally difficult to spot in the field, so I’m impressed by the discovery and that the authors recognised the significance of their find.”