Produced by the Population Genetics and Evolution class, Furman University

The Carboniferous: Psaronius
Psaronius is a genus of extinct giant tree ferns. They grew between 10-15 meters in length and possessed helically arranged leaves between 2-3 meters long and exhibited large, vertically elongated leaf scars on the apex of their central strand (Steur 2008, Rothwell 1982). Curiously, these ferns did not undergo secondary growth formation necessary to produce a woody stem. Instead, they formed advantageous root mantels for stability which also caused the base of the trunk to broaden for additional support (Steur 2008). These stems were between 3.6-14.2 centimeters in diameter and were arranged internally in 3-6 stelar cycles that were separated by aerenchymatous ground tissue and surrounded by a peripheral sheath for protection and support (Rothwell 1982). An interesting side note was that additional epiphytic ferns would grow on these root mantles and not drain resources from its parental host (Steur 2008).

Page by Iggy Gaska
Cross section of a tree fern revealing cellular trunk details. Photo from: The Natural History Museum of London

National History Museum.2008. Psaronius brasiliensis Brogniart, fossil true fern. Accessed March 3, 2010.

Rothwell GW. Blickle AH.1982.Psaronius Magnificus n. comb., A Marratticlean Fern from the Upper Pennsylvanian of North America. Journal of Paleontology. 56: 459-468.

Steur H.2008. Psaronius. Hans’ Paleobotany page. Accessed March 2, 2010.