Phylloceras Ammonoidea (Ammonite Section)
Phylloceras cf. serum • Body fossil/Cast; Invertebrate Cephalopod
Geological Period
Jurassic to Cretaceous
Estimated Age
66 to 201 million years
Preservation Type
Mineral replacement and internal mold development with calcareous infilling
Condition Assessment
Fair; the specimen is partially embedded in matrix, weathered by water action, and lacks complete shell preservation
Taxonomic Classification
Phylum: Mollusca, Class: Cephalopoda, Order: Ammonitida, Family: Phylloceratidae, Genus: Phylloceras
Morphological Description
The specimen shows a partial cross-section and external cast of a planispiral shell. Notable features include fine, complex 'phylloceratid' suture lines (leaf-like patterns) visible on the weathered surface, indicating a high degree of septal folding.
Rock Matrix
Dense calcarenite or silty limestone with organic staining and algal growth from the underwater environment
Formation & Location
Commonly found in the Tethyan realm deposits, such as the Agadir Basin (Morocco) or the Jurassic Coast (UK)
Size & Dimensions
Approximately 8-12 cm in diameter based on visible arc curvature, typical for medium-sized phylloceratid specimens
Value & Rarity
Estimated Market Value
$30 - $70 USD (In situ/unprepared)
Auction Estimate
$50 - $150 USD (If professionally extracted and prepared)
Rarity Assessment
Common; while the genus is widely distributed, well-preserved suture patterns are always of interest to collectors
Scientific Significance
Ammonites are vital index fossils for biostratigraphy. Phylloceratids are significant for studying the evolution of cephalopod buoyancy and their survival through extinction events.
Preparation Recommendations
Mechanical preparation using an air-scribe would be required to remove the surrounding matrix. Desalination is necessary if recovered from a saltwater environment.
Notable Features
The presence of intricate, dendritic suture lines resembling fern leaves, which is the diagnostic hallmark of the Phylloceratidae family.
Notes
Underwater