Fossilized Fish Nodule (Coelacanth or Osteichthyan scale/body fossil)
Osteichthyes indet. cf. Sarcopterygii • Body fossil, vertebrate preserved as a concretion mold and cast pair
Geological Period
Carboniferous or Permian
Estimated Age
290 to 360 million years ago
Preservation Type
Mineral replacement and impression within a siderite or ironstone concretion (nodule preservation)
Condition Assessment
Good. A complete matching pair (part and counterpart) showing clear scale ornamentation, though some surface weathering and mineral encrustation obscure finer cranial details.
Taxonomic Classification
Phylum Chordata, Subphylum Vertebrata, Class Osteichthyes
Morphological Description
The specimen displays a spindle-shaped or ovate concretion split into a positive and negative half. Distinct, regular rectangular to rhombic scale patterns (resembling ganoid or cosmoid scales) are clearly visible over the body cavity, along with a distinct head/skull region at the anterior end showing internal bone structure.
Rock Matrix
Ironstone / clay-ironstone concretion with limonitic and hematitic weathering, typical of freshwater or estuarine nodules
Formation & Location
Mazon Creek Formation, Illinois, USA or similar contemporaneous Carboniferous-Permian Lagerstätten globally
Size & Dimensions
Approximately 5 to 7 cm in length for the nodule, fitting within the small-to-medium size range for juvenile or small-bodied Paleozoic fish
Value & Rarity
Estimated Market Value
$50 - $150
Auction Estimate
$40 - $100
Rarity Assessment
Uncommon
Scientific Significance
Provides valuable insight into Paleozoic aquatic ecosystems, scale morphology, and the tapinogeneration of soft-bodied or heavily scaled vertebrates in concretionary environments.
Preparation Recommendations
Keep dry and stable. Mechanical preparation under a microscope using a fine air scribe or pin vise could potentially reveal more cranial detail, but care must be taken due to the fragile ironstone matrix.
Notable Features
Excellent preservation of the reticulated, geometric scale pattern in direct part-and-counterpart halves, featuring distinct reddish-brown iron oxide coloration.