Calamopityaceae
[6] However, nothing is known of their reproductive organs, but they are classified as seed plants based on their similarities to the Lyginopteridaceae and Medullasaceae families within Pteriodspermatophyta.[4][5] To identify a genus within this family, this petiole structure and monoxylic wood must be present, as well as a much larger cortex than vascular cylinder.[1] Calamopityaceae fossils have been found in North America and Europe, and they have been dated back to the Paleozoic era, specifically the Upper Devonian and Lower Carboniferous (Mississippian) periods.[4][5] In 1856, the Austrian paleontologist, Franz Joseph Andreas Nicolaus Unger, was the first to find Calamopitys, a genus of Calamopityaceae.[11] Three genera of fossil wood are currently classified as belonging to the family Calamopityaceae, and their differences are distinguished by their decreasing primary xylem from Stenomyelon, to Calamopitys, to Diichnia.[6] Although Eristophyton is sometimes considered to be a subgenus under this genus, the distinction between pycnoxylic and monoxylic secondary wood maintains these genera as separate.