Stigmaria (Scale Tree Root)
Stigmaria ficoides (the most common form-taxon for these arborescent lycopsid roots) • Trace/Body Fossil (Cast/Mold) of a Lycopodiophyta (Ancient Club Moss) root system
Geological Period
Carboniferous (Pennsylvanian sub-period)
Estimated Age
298 to 359 Million Years
Preservation Type
Cast and mold preservation with secondary permineralization; the internal organic structure has been replaced by sediment which hardened into rock.
Condition Assessment
Good; the specimen is large and displays clear diagnostic surface features on one side, though it appears to be a partial fragment with some weathered edges and loss of detail near the break points.
Taxonomic Classification
Kingdom: Plantae, Division: Lycopodiophyta, Class: Isoetopsida, Order: Lepidodendrales, Genus: Stigmaria
Morphological Description
The specimen displays a cylindrical to semi-compressed form with a characteristic pattern of circular to oval indentations or 'pocks'. These are rootlet scars (stigmatic scars) arranged in a spiraling pattern where lateral rootlets once branched out. The surface texture is somewhat leathery or granular, typical of the outer cortex of these carboniferous plants.
Rock Matrix
Dense Sideritic Ironstone or fine-grained Siltstone with possible carbonaceous inclusions and iron oxide staining (noted by the reddish-orange patches).
Formation & Location
Commonly found in the 'Coal Measures' of North America (e.g., Pottsville Formation, Appalachian Basin) and Europe (e.g., South Wales or Northern England Coalfields).
Size & Dimensions
Approximately 12-16 inches in length based on floorboard perspective; this represents a significant segment of a primary root branch from a tree that could reach 100 feet in height.
Value & Rarity
Estimated Market Value
$100 - $250 USD
Auction Estimate
$150 - $350 USD
Rarity Assessment
Uncommon; while Stigmaria fragments are found frequently in coal-bearing regions, specimens of this size and weight with clear patterning are more desirable for collectors.
Scientific Significance
Stigmaria are critical for understanding the 'Coal Forest' ecosystems. They demonstrate how ancient giant lycopsids anchored themselves in swampy, waterlogged soils using a dichotomously branching rooting system rather than a deep taproot.
Preparation Recommendations
Keep dry and away from high humidity to prevent oxidation of iron minerals. Professional cleaning with a soft brush and stabilization with a dilute archival consolidant (like Paraloid B-72) could enhance the contrast of the rootlet scars.
Notable Features
The specimen features a very clear spiral arrangement of scars, and the iron-rich mineralization has provided a pleasing color contrast against the dark grey matrix. The tapering shape suggests it may be toward the distal end of a primary root bifurcation.