Before Trees, Earth Had 24-Foot Prototaxites Spires

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About 400 million years ago, Earth looked nothing like the wooded world we know today. Land plants were still small, yet enormous trunk-like structures called Prototaxites could rise roughly 24 feet high and reach about 3 feet across. Their fossils have puzzled scientists since the nineteenth century because they lack the leaves, branches, roots, and ordinary wood expected from a tree. For much of modern research, Prototaxites was treated as a giant fungus or fungus-like organism. Evidence from its chemistry supported the idea that it did not feed by photosynthesis in the same way plants do. However, the identity of Prototaxites has never been completely settled. Recent research on exceptionally preserved fossils has raised new problems for the fungal explanation, including unusual internal structures and chemical signatures that do not fit known groups. Researchers have therefore considered the possibility that Prototaxites belonged to an extinct branch of complex life with no living descendants. That uncertainty is what makes the fossils especially fascinating. The familiar image of a giant mushroom towering over a treeless landscape captures the scale of the organism, but it should not be treated as a settled identification. What is clear is that these strange structures were among the largest things living on land long before forests became a familiar part of Earth.