Fossil rhizome (Stigmaria)

Fossils of the genus Stigmaria are rhizomes or roots produced by plants belonging to the taxon of the lycophytas. These rhizomes have obvious scars on the surface characterized by the presence of a helical umbilicus, the site of insertion of the absorbing roots. The Lycophytales are an order of plants that have no wood but, despite this, could attain arboreal bearing because of a thickening of the bark.
The stem produced linear and elongated leaves, inserted directly into the trunk and branches. The scar left by the fall is the morphological criterion used to classify the different species.