Trilobite (Partial Cephalon)
Phacops sp. or Dalmanites sp. (cf. Phacopoid) • Body fossil; Invertebrate (Arthropod)
Geological Period
Ordovician to Devonian
Estimated Age
Approx. 360 - 480 million years
Preservation Type
Replacement and carbonization; the darker central area suggests organic residue or mineral replacement within a fine-grained sedimentary cast.
Condition Assessment
Fair; the specimen is incomplete, missing the thorax and pygidium, and shows significant surface erosion/weathering.
Taxonomic Classification
Phylum: Arthropoda; Class: Trilobita; Order: Phacopida (likely); Family: Phacopidae or Dalmanitidae
Morphological Description
A partial cephalon (head section) displaying a prominent central glabella with visible furrows and a rounded anterior margin. Portions of the fixigenae (fixed cheeks) are present, though the specimen appears weathered and lacks clearly defined compound eyes or genal spines.
Rock Matrix
Silty mudstone or fine-grained shale, light grey to tan in color, consistent with typical trilobite-bearing deposits.
Formation & Location
Likely sourced from the Hamilton Group (New York, USA), the Jorf or Alnif regions (Morocco), or similar Paleozoic marine formations.
Size & Dimensions
Approx. 4-6 cm in width; typical of mid-sized Paleozoic benthic trilobites.
Value & Rarity
Estimated Market Value
$15 - $40 USD
Auction Estimate
$20 - $50 USD
Rarity Assessment
Common; trilobite fragments of this genus and preservation quality are widely distributed in the fossil record.
Scientific Significance
Provides evidence of Paleozoic marine benthic ecosystems and arthropod diversification; useful for local stratigraphic correlation within its original formation.
Preparation Recommendations
Keep in a low-humidity environment; no further mechanical preparation recommended as it may damage the soft matrix; display in current shadow box to prevent further breakage.
Notable Features
The distinct color contrast between the glabella and the surrounding matrix suggests selective mineralization or the presence of a carbonaceous film.