Cretaceous Ray Mouth Plate Fragment
cf. Myliobatis sp. or Rhombodus sp. • Body fossil (vertebrate); Chondrichthyes (cartilaginous fish) dental pavement
Geological Period
Cretaceous Period (likely Late Cretaceous)
Estimated Age
66 to 100 million years
Preservation Type
Mineral replacement (permineralization), likely by phosphate and iron oxide giving the dark, lustrous appearance.
Condition Assessment
Good; the specimen is an isolated fragment rather than a complete mouth plate. The grinding surface is well-preserved, and the basal vascular structure is clearly visible.
Taxonomic Classification
Phylum: Chordata, Class: Chondrichthyes, Order: Myliobatiformes, Family: Myliobatidae (Eagle Rays) or Rhombodontidae
Morphological Description
A rectangular to hexagonal section of a dental pavement. It features a distinctive 'sandwich' structure with a smooth, dark occlusal (grinding) surface and a porous, vascularized root structure beneath. The grinding surface is dense and shows wear from crushing hard-shelled prey.
Rock Matrix
Absent (isolated specimen); typically found in phosphate-rich bone beds, marine sands, or marls.
Formation & Location
Commonly found in the Late Cretaceous phosphate deposits of Morocco (Ouled Abdoun Basin) or the Atlantic Coastal Plain of North America.
Size & Dimensions
Approximately 1.5 cm to 2.5 cm in length, which is a standard size for a partial segment of a ray's tooth bar.
Value & Rarity
Estimated Market Value
$5.00 - $15.00 USD
Auction Estimate
$10.00 - $20.00 USD (typically sold in larger lots)
Rarity Assessment
Common; ray teeth are highly durable and abundant in Cretaceous and Paleogene marine deposits globally.
Scientific Significance
Provides evidence of specialized durophagous (shell-crushing) feeding strategies in Mesozoic marine ecosystems. Useful index fossils for correlating marine strata.
Preparation Recommendations
No extensive preparation required. Surface cleaning with a soft brush and distilled water. Maintain in a dry environment to prevent possible pyrite oxidation if present.
Notable Features
The high contrast between the dense, dark enameloid grinding surface and the highly porous, sponge-like root architecture is a hallmark diagnostic feature of elasmobranch dental elements.