Armored Fish Scale Patch / Placoderm Plate
Placodermi indet. cf. Holonema or Osteichthyes indet. scale patch • Vertebrate body fossil, specifically an articulated dermal bone armor plate or scale-covered integument of a primitive jawed fish
Geological Period
Devonien
Estimated Age
359 to 419 million years ago
Preservation Type
Permineralization and direct replacement of original dermal bone material within a consolidated concretion
Condition Assessment
Good. The geometric grid of scales is well-preserved centrally, though some surface weathering and mineral encrustation (white patches) obscure parts of the periphery, and the margins are naturally fractured along the nodule outline.
Taxonomic Classification
Phylum: Chordata, Subphylum: Vertebrata, Infraphylum: Gnathostomata, Class: Placodermi (or stem-Osteichthyes/Sarcopterygii)
Morphological Description
The specimen exhibits a clearly defined, highly ordered mosaic of rectangular to rhomboidal scutes or bony scales tightly articulated in a grid-like pattern. Surface ornamentation shows fine parallel ridges and reticulated textures typical of ancient dermal bone. A distinct terminal or central bony element, possibly a skull roof fragment, plate margin, or joint, is visible at the upper pole.
Rock Matrix
Iron-rich fine-grained sandstone to siltstone concretion, heavily oxidized with brown and reddish-orange limonite/hematite staining
Formation & Location
Old Red Sandstone formations (UK), or Catskill Delta Formation (USA), or equivalents in Europe and North America known for Devonian fish beds
Size & Dimensions
Approximately 8 to 12 cm in length, fitting well within typical scale patch specimens for mid-sized Devonian armored fish
Value & Rarity
Estimated Market Value
$100 - $300
Auction Estimate
$150 - $250
Rarity Assessment
Uncommon
Scientific Significance
Provides valuable insight into the dermal skeleton evolution, scale morphology, and squamation patterns of early jawed vertebrates during the Age of Fishes
Preparation Recommendations
Mechanical preparation under a stereo microscope using an air scribe at low pressure to clear away matrix obscuring scale edges; stabilization with a dilute PVA or Butvar B-76 consolidant; store in a dry environment to prevent pyrite disease if sulfur compounds are present.
Notable Features
The exceptionally clear, brick-like regularity of the articulated scale rows and the contrasting white mineral infill highlighting the structural boundaries of the dermal armor.