Wikipedia
Callistophytaceae
The Callistophytaceae was a family of seed ferns ( pteridosperms) from the Carboniferous and Permian periods. They first appeared in late Middle Pennsylvanian (Moscovian) times, 306.5–311.7 million years ago ( Ma) in the tropical coal forests of Euramerica, and became an important component of Late Pennsylvanian (Kasimovian-Gzhelian; 299.0–306.5 Ma) vegetation of clastic soils and some peat soils. The best known callistophyte was documented from Late Pennsylvanian coal ball petrifactions in North America.