Stigmaria is a form genus for tree roots of Carboniferous coal forest Lycopod
trees such as Sigillaria and Lepidodendron.
appear in the fossil record in the
Silurian in conjunction with many other vascular
plants, and led to the trees that would dominate the equitorial
landscape in the Mississipian and Pennsylvanian periods.
North America was at the equator during the Carboniferous
(290 to 359 million years ago). There were extensive, hot
forests with Pteridospermatophyta (seed ferns) and huge Lycopodiophyta
trees, Sigillaria and Lepidodendron, some on the order
of 30 meters
tall with trunks a meter or more thick.
Unlike modern trees, lycopid tree leaves grew along the full
extent of the trunk and branches, falling off as the plant grew,
but a small cluster of leaves at the top. These forests
became the coal seams we mine for fuel in moderm times; stigmaria
often impregnated with coal, or have coal sticking to their surface.
Note the round nodes on the surface of this fossil, which is
where small roots grew out in all radial directions.
fossil comes from a very old collection, some 50 to 60 years
old, which was the plant fossil collection of a man and wife
team who combed more than 100 plant fossil sites, almost all
west of the
River. No doubt, some of these sites have been subsumed by strip
malls, and urban sprawl, or are otherwise no longer open
to collecting. There was no Internet for these amature collectors
to research their treasures, so many plant fossils were unidentified.