Alethopteris sp.-Pennsylvania 5

Identification: Alethopteris sp.

Age: Pennsylvanian-Carboniferous

Geology: Llewellyn formation

Locality: St. Clair, Pennsylvania

St. Clair ferns

St. Clair, Pennsylvania fern fossils are famous Pennsylvanian-age plant impressions preserved in black shale, often showing bright white outlines from mineral replacement. They commonly include ferns such as Alethopteris, Neuropteris, and Pecopteris. These fossils formed in ancient swampy environments, where plant material was buried, compressed, and mineralized over time.