Rare 3D fossil discovery sheds light on unusual shapes of early trees

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Newly discovered tree fossils from New Brunswick, Canada, are rewriting the story of ancient trees, revealing features never before seen. 

The fossils, which include an unexpected three-dimensional crown structure, provide a unique glimpse into the morphology of trees dating back 350 million years. This fossilized tree species has been scientifically named Sanfordiacaulis densifolia.

“The way in which this tree produced hugely long leaves around its spindly trunk, and the sheer number over a short length of trunk, is startling,” said Robert Gastaldo of Colby College in Waterville, Maine.

This fossil finding is important, especially given that most trees are only preserved as trunks, with no indication of canopies or overall forms.

According to the press release, the preservation of this fossil occurred due to its burial in an ancient rift lake induced by an earthquake.

The ancient tree looked like ferns

The recently discovered ancient tree resembles ferns or palms, which makes it a surprising discovery as palms appeared much later in the known record. 

However, unlike ferns and palm trees, which have fewer leaves at the top, the fossilized tree has over 250 leaves along its stem.

“In contrast, Sanfordiacaulis preserves more than 250 leaves around its trunk, with each partially preserved leaf extending 1.75 meters from it,” Gastaldo said. 

Gastaldo added, “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.”

The researchers posit that Sanfordiacaulis represents the earliest documented evidence of smaller trees thriving beneath a taller forest canopy. Moreover, it provides remarkable evidence of diverse plant life in the Early Carboniferous epoch. 

“We all have a mental concept of what a tree looks like, depending on where we live on the planet, and we have a vision of what is familiar,” Gastaldo said.

“The fossil on which we report is unique and a strange growth form in the history of life. It is one of evolution’s experiments during a time when forest plants underwent biodiversification, and it is a form that seems to be short-lived,” Gastaldo concluded in the press release.

The findings were published in the journal Current Biology.

Study abstract:

The evolution of arborescence in Devonian plants, followed by their architectural radiation in the Carboniferous, is a transition fundamental to Earth-system processes and ecological development. However, this evolutionary transition in trees is based on preserved trunks, of which only a few known specimens possess crowns. We describe Mississippian-aged (Tournaisian) trees with a unique three-dimensional crown morphology from New Brunswick, Canada. The trees were preserved by earthquake-induced, catastrophic burial of lake-margin vegetation. The tree architecture consists of an unbranched, 16-cm-diameter trunk with compound leaves arranged in spirals of ~13 and compressed into ~14 cm of vertical trunk length. Compound leaves in the upper ~0.75 m of the trunk measure >1.75 m in length and preserve alternately arranged secondary laterals beginning at 0.5 m from the trunk; below the trunk bears only persistent leaf bases.