Carboniferous Sigillaria (Clubmoss) Plant Fossil

This is a beautiful fossil of the extinct club moss Sigillaria rugosa from the Upper Silesia Coal Basin of Poland. It's Upper Carboniferous in age or approximately 305 million years old. This fossil plant, resembling tire tread is preserved on both sides of the rock, and gives a glimpse into the past a plant that must have looked very alien-like.

While Sigillaria would have resembled a large tree, these plants were not actually classified as trees. The clubmoss trees of the genus Sigillaria formed an important part of the coal swamps in the Late Carboniferous. They grew to large heights, probably exceeding 100 feet and had trunks/stems over 2 meters in diameter.

It did not have "wood" like trees, and support came from a layer of closely packed leaf bases just below the surface of the trunk, while the center was filled with pith. The old leaf bases expanded as the trunk grew in width, and left a diamond-shaped pattern, which is evident in fossils. The trunk had photosynthetic tissue on the surface, meaning that it was probably green. The trunk was topped with a plume of long, grass-like, microphyllous leaves, so that the plant looked somewhat like a tall, forked bottlebrush. The plant bore its spores (not seeds) in cone-like structures attached to the stem. Sigillaria, like many ancient lycopods, had a relatively short life cycle - growing rapidly and reaching maturity in a few years.