Polished Gastrolith / Dinosaur Stomach Stone
Indeterminate dinosaur gastrolith (cf. sauropod or large ornithopod) • Trace fossil (gastrolith), vertebrate classification
Geological Period
Mesozoic (Cretaceous or Jurassic)
Estimated Age
66 to 145 million years old
Preservation Type
Silicification and mechanical wear/polishing via gastric milling
Condition Assessment
Good condition, complete natural trace fossil showing classic rounded digestive wear with minor surface weathering
Taxonomic Classification
Ichnofamily: Gastrolith; Vertebrate-associated trace fossil
Morphological Description
Sub-cylindrical to elongated oval shape with noticeably rounded, smooth, water-worn or gizzard-ground surfaces, exhibiting subtle striations and a dull polish characteristic of mechanical abrasion inside a herbivorous dinosaur's digestive tract.
Rock Matrix
Dense igneous or metamorphic river-worn pebble matrix (quartzite or similar durable lithology)
Formation & Location
Morrison Formation (North America) or equivalent continental dinosaur-bearing fluvial deposits worldwide
Size & Dimensions
Approximately 10 to 15 cm in length, consistent with medium-to-large gastroliths found associated with sauropod or large ornithischian remains
Value & Rarity
Estimated Market Value
20 to 50 USD
Auction Estimate
15 to 40 USD
Rarity Assessment
Common, though genuine dinosaur-associated gastroliths require specific geological context to confirm authenticity over river pebbles
Scientific Significance
Provides direct evidence of herbivorous dinosaur digestive processes, diet, and physiological use of stones for mechanical breakdown of plant material, as well as behavioral clues regarding ingestion and transport
Preparation Recommendations
No intensive preparation required; clean gently with warm water and mild soap, store in a dry environment with proper provenance documentation
Notable Features
Uniform elongated shape with smooth, frictionless facets typical of prolonged internal gizzard grinding before deposition in a terrestrial sediment layer