Ancient ‘Alien Plant’ Fossil Challenges Classification, Revealing a Unique Lineage in Plant Evolution

Fifty-five years ago, researchers discovered a plant fossil near a Utah ghost town and named it Othniophyton elongatum, or “alien plant.” Based on the fossilized leaves, scientists initially speculated that the plant might be related to the ginseng family. However, this hypothesis was formed with limited evidence, as no additional parts of the plant, such as flowers or fruits, were available for study at the time.

Decades later, Steven Manchester, a paleobotanist at the Florida Museum of Natural History, found a second fossil of the plant in a collection at the University of California, Berkeley. Unlike the original discovery, this fossil was much more complete, featuring leaves, flowers, and fruits. Both fossils were excavated from the Green River Formation, a site dating back 47 million years when the region was a lake ecosystem surrounded by volcanic activity. The unique preservation conditions in this environment left the plant remarkably intact.

The more complete fossil revealed traits that contradicted the initial ginseng connection. The arrangement of flowers and fruits, along with the detailed structure of the leaves, showed significant differences from plants in the ginseng family. When Manchester’s team compared the fossils to over 400 living families of flowering plants and various extinct groups, they found no matches, suggesting the plant belonged to an entirely distinct lineage.

Newer technologies, including high-resolution microscopy and artificial intelligence, enabled scientists to examine the plant fossils in greater detail. The researchers identified features such as tiny seed impressions and persistent stamens—reproductive structures that typically detach in most flowering plants after fertilization. These traits set the fossil apart from both modern and extinct plants, highlighting its uniqueness within the plant kingdom.

The Green River Formation has previously produced other surprising plant fossils, such as Bonanzacarpum fruit and Palibinia leaves, which led to the identification of extinct plant groups. The discovery of the “alien plant” continues this pattern of uncovering ancient species that do not fit within known classifications, broadening our understanding of plant evolution and ancient ecosystems.