Mazon creek is one of the world's Lagerstatten site noted for exquisite fossil preservation, even soft tissue. The fossils are usually in ironstone nodules that were formed due to coverage in mud and the action of bacteria. Over 400 species from at least 130 genera of flora have been identified from Mazon Creek nodules

Annularia is a genus for calamitalean foliage. The narrow lancet-like Annularia leaves are placed in whorls, positioned at the nodes. All leaves lie in one plane and the whorls are circular to oval in outline. Several dozens of species are distinguished. The distinguishing identification feature other than size is that the radiata is at it's widest point at the center of each leaf while the stellata is widest closest to the tip.