Earliest Glimpse at Forest Understory: Rare 3-D Tree Fossil Discovered

The Sanfordiacaulis densifolia tree, with its spiraled top and thin trunk, appears to have jumped right out from Dr. Seuss' The Lorax. However, despite its whimsical appearance, it isn't simply a real-life version of a truffula. Rather, it’s a three-dimensional rendering of a 350-million-year-old fossil offering a rare glimpse into plant history thanks to its preserved trunk and leaves. This find was reported on February 2 in Current Biology.

Geologist Robert Gastaldo of Colby College in Waterville, Maine, was astonished when he first encountered the fossil. The rarity of such a find led him to equate its occurrence to winning a lottery.

In a span of seven years, researchers have unearthed five S. densifolia specimens. All these fossils were located near what was once a lake in New Brunswick, Canada. The trees originate from a relatively obscure era in plant history referred to as the early Mississippian. Interestingly, this newly found fossil's modest height, coupled with the preserved trunk and crown, hint at the probable existence of more layers in Mississippian forests than previously assumed. It ranks as the most complete tree fossil from this era and one of the very few with such traits found throughout geological history.

Botanist Mihai Tomescu of California State Polytechnic University, Humboldt, who was not part of this study, hailed the discovery as "remarkable" as it fills a void in our understanding of forest structure during the Mississippian time.

Scientists believe that these trees were probably knocked down by an earthquake, ending up at the base of a nearby lake where they were subsequently preserved. But unlike most fossils, the newly discovered specimen was not flattened. The tree amazingly retained its three-dimensional structure, which biologist Patricia Gensel of the University of North Carolina at Chapel Hill states is rare.

Researchers used Blender, a computer graphics programme, along with the fossil to develop a digital 3-D reconstruction of the tree's likely appearance. Though it was seemingly half the height of an adult giraffe, the tree bore a large crown and possibly had leaves about 3 meters long. Despite uncertainty over whether the tree was fully grown, researchers anticipate it wouldn't have approached the height of other trees known from the Mississippian era, some of which could have towered over 20 meters.

The tree's comparative middling height and sizeable leaves propelled researchers to consider the S. densifolia as the earliest potential evidence of a subcanopy tree, which would confer a layered structure to forests. To survive in the subcanopy, trees would have relied on their large leaves to absorb as much sunlight as possible. Gastaldo notes that the forest layer's establishment could have resulted in new ecosystems, thereby increasing biodiversity.

Uncovering more S. densifolia fossils can illuminate how plants adapted over time. "Understanding the transformations undergone by plants throughout time assists us in predicting how they might adapt to survive in the future," says Gensel.