Fossilized 350 Million-Year-Old Trees Uncovered in Canada

Sanfordiacaulis model with simplified branching structure

Sanfordiacaulis model with simplified branching structure. Image Credit: Tim Stonesifer

You won’t be-leaf the shape of this ancient tree. A team of researchers found a 350-million-year-old fossilized tree species that looks like something out of Dr. Seuss.

The fossils are some of the oldest-known trees and were discovered in what was once an ancient lake in northeastern Canada. The species is called Sanfordiacaulis densifolia and would have taken up residence under the taller members of the forest canopy. The earliest fossil trees date back to the late Devonian Period, and these—from the early Carboniferous—are just a few million years younger. It’s not clear what Sanfordiacaulis’ closest relations are on the tree of life (no pun intended), which means it’s incertae sedis—an enigmatic taxa.

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

Researcher Olivia King with the newly discovered fossil. Image Credit: Matt Stimson

The team thinks that the fossils were preserved because of an earthquake that caused these trees to be buried along the margin of a rift lake. One specimen was discovered seven years ago, and now four more complete specimens of the same plant found nearby have been unearthed as well. One of the specimens shows how the leaves departed from the tip of the tree.

“Any fossil tree with an intact crown is a rarity in the history of life,” Gastaldo said. “Having the crown leaves attached to a trunk, by itself, begs the questions what kind of plant is it, how is that plant organized, And is it some form that continues to the present, or is it outside of the ‘normal’ concept of a tree? All of these questions, and more, led to this multi-year endeavor.” 

Why the tree might have had such an unusual leaf arrangement is still up for debate. The researchers think it could be that the leaves were so long in order to capture as much light as possible so the plant could outcompete other smaller plants in the same habitat. The team thinks this is some of the earliest evidence of trees growing at different levels, known as sub-canopy-tiering. 

“The history of life on land consists of plants and animals that are unlike any of those that live at the present,” Gastaldo said. “Evolutionary mechanisms operating in the deep past resulted in organisms that successfully lived over long periods of time, but their shapes, forms, growth architectures, and life histories undertook different trajectories and strategies. Rare and unusual fossils, such as the New Brunswick tree, is but one example of what colonized our planet but was an unsuccessful experiment.”

This spectacular and unusual fossil reveals that vegetation in the Early Carboniferous was much more complex than previously thought. If you can’t get enough of plants doing something a bit unexpected, check out these zombie ferns.

The paper is published in the journal Current Biology.

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