Trilobite Cephalon (Lower Head Shield)
cf. Phacops rana or Drotops megalomanicus • Body fossil (Invertebrate/Arthropod)
Geological Period
Middle Devonian (likely Eifelian or Givetian stages)
Estimated Age
380 - 395 Million Years
Preservation Type
Replacement/Recrystallization. The exoskeleton appears replaced by darker minerals (likely silica or calcite) against a lighter matrix.
Condition Assessment
Fair condition. It is an incomplete specimen consisting only of the head shield; the thorax and pygidium are missing. The surface shows some erosion and tool marks from rough extraction.
Taxonomic Classification
Phylum: Arthropoda, Class: Trilobita, Order: Phacopida, Family: Phacopidae, Genus: Phacops (or Drotops)
Morphological Description
A dorsal view of a trilobite cephalon, specifically the glabella and surrounding fixigenae. The glabella shows a characteristically rounded, inflated shape typical of the Phacopidae family, with visible granulation on the surface. Small crescentic structures suggesting schizochroal eyes are partially visible on the lateral margins.
Rock Matrix
Hardened, weathered limestone or calcarenite with some iron oxide staining visible at the bottom fracture.
Formation & Location
Commonly found in the Hamilton Group (USA/Canada) or the Maïder Region (Morocco). Given the morphology, a Moroccan origin is highly probable.
Size & Dimensions
Approximately 4-6 cm in width; this is a large specimen size for a Phacopid cephalon, suggesting a mature individual.
Value & Rarity
Estimated Market Value
$25.00 - $55.00 USD
Auction Estimate
$20.00 - $40.00 USD
Rarity Assessment
Common. While Phacopids are iconic, isolated cephala are frequent finds and widely available on the commercial market.
Scientific Significance
Provides a window into Devonian marine benthic communities. Phacopid trilobites are essential index fossils for stratigraphic dating and studying the development of complex compound eyes.
Preparation Recommendations
The specimen should be kept in a low-humidity environment to prevent further weathering. Mechanical preparation with an air scribe could potentially reveal more detail on the eye lenses if they are still embedded in the matrix.
Notable Features
The distinct inflation of the glabella and the 'frog-like' facial appearance characteristic of the Phacops genus are prominent features, emphasizing the defensive enrolling capabilities of this organism.
Notes