During the late Devonian times, we find moist mountains extending from Georgia to Newfoundland with many streams that flowed westward to the retreating sea. Where these streams reached the sea, they built up deltas, which spread until they formed an almost continuous lowland covered by some of the earth’s first forests. Fossils from these forests are scattered from Gilboa, New York along the southern part of Ohio, through Indiana, to Oklahoma to Yellowstone Park (Beartooth Butte) and on to Russia. These forests extended northward into Canada and as far south as northern Alabama and Mississippi. Most of this fossil wood belongs to Callixylon Newberryi.
However, the Devonian Period came to an abrupt end as rocks crumpled into mountain ranges. The early Carboniferous (Mississippian) period, which was to last 30,000,000 years, began; and shallow seas once again spread widely across North America. Lycopods, ferns, seed ferns, and trees related to Callixylon grew profusely, but few fossil remains with much detail are left.
The most satisfying picture of the Carboniferous plant life is found in the next division of the earth’s history, the Pennsylvanian or “Coal Age”. This period saw seas repeatedly advance and disappear forming a vast series of swamps which were a paradise for plant life. As these plants died, they formed huge beds of peat, which hardened into coal. Besides beds of coal, an abundance of fossils were left for us, so many as to defy the imagination. Some are mere impressions in standstone, but many are perfect
petrifications found in lumps of calcite or “coal balls”, which are found throughout the world wherever coal seams are unearthed.
The most prominent of these trees was the Lepidodendron (a lycopod) with a trunk growing 100 to 125 feet tall and bearing diamond-shaped scars arranged in a spiraling fashion around the truck where leaves like overgrown pine needles had grown.
The next most important tree of this period was the Sigillaria, which was much shorter than the Lepidodendron but much thicker at the base. The species most common in this area (Tennessee and Alabama) had vertical ridges of bark running the length of the trunk or limb with leaf scars on these ridges which resembled the eyes of an Irish potato.
Another fossil wood of this period was the Cordaites (pronounced Kor-da-ee-teez). It is distinctly related to the pines and stands close to the Callixylon of the late Devonian forests. The Cordaites had wider, thinner and less pointed leaves than the lycopods. Flattened heart-shaped seeds were borne on stalks among the leaves.
Ancestors of the modern horsetails or scouring rushes contributed much to the coal bed of our area. The Calamites, our chief Pennsylvanian genus, grew to as much as 40 feet tall. It had fine verticle ridges running the length of the stem, limb, or root. These had rings around them where small branches or leaves were attached as if in clusters around the stems or branches