Before trees existed 360 to 430 million years ago, 26-foot-tall, tower-like organisms called prototaxites dominated Earth’s landscape. Canadian geologist William Edmond Logan first discovered these log-like tower fossils in Quebec, Canada, in 1843. Initially thought to be a complex fungus, scientists struggled to classify them within the existing framework of life on Earth.

New research in Science Advances asserts that prototaxites are a previously undiscovered branch of life that is now extinct. The study of a well-preserved tower fossil found in Scotland revealed an unusual physical structure and a distinct chemical fingerprint, ruling out it being a fungus and excluding it from other known genera. Further analysis is needed to conclusively determine that prototaxites are a unique life form.