Millions of years before the first trees grew their canopies and the earliest insects buzzed, a strange organism sprouted from the ground. It looked like a trunk, cylindrical and bare, stretching over 20 feet into the Devonian sky. But it had no leaves. No branches. No clear kin. For nearly two centuries, paleontologists argued about what this bizarre life-form was.

Now, new research suggests Prototaxites — long thought to be a colossal fungus — may have belonged to a completely unknown chapter in the story of life on Earth. Not a plant, not an animal, and not a fungus — but something entirely different.

After extensive research dating back to the 1840s, scientists recently concludes that Prototaxites likely belonged to “a previously undescribed, entirely extinct group of eukaryotes.”

In the grand tree of life, that’s a big claim. Eukaryotes — organisms with complex cells — include animals, plants, fungi, and protists. But this ancient tree-like giant, the researchers argue, fits in none of these categories. It stands apart.

A new kingdom of life unknown to science wouldn’t be out of question. Nature has experimented wildly throughout Earth’s history. Many ancient lineages have disappeared without leaving living descendants. 

It's possible the organism may have been “a novel experiment with complex multicellularity that is now extinct.” It may not have photosynthesized like a plant. It didn’t decompose like a mushroom. And it certainly didn’t walk, swim, or crawl. But it grew. It fed. It thrived for tens of millions of years. Then it vanished.