Gastrolith
A stone swallowed and retained in an animal’s digestive tract. Gastroliths can help grind food or serve other digestive functions.
Gizzard: A muscular digestive organ that mechanically breaks down food, especially in birds. Birds use gastroliths inside the gizzard to help grind food.
Bird: A feathered, warm-blooded vertebrate in the class Aves. Many birds swallow stones that collect in the gizzard and help process food.
Dinosaur gastroliths: Stones found in association with dinosaur fossils and proposed to have been swallowed during life. These finds illustrate both proposed digestive uses and the difficulty of proving function.
Gastrolith identification: The evaluation of whether a stone associated with a fossil was swallowed by the animal. Shape, polish, location, and geological context all affect whether a fossil stone qualifies.
Bird digestion: The processes by which birds ingest, break down, absorb, and eliminate food. Gastrolith use is one part of the digestive adaptations found in birds.
Crocodile: A large semiaquatic reptile in the family Crocodylidae. Crocodiles may ingest stones, though their digestive role remains debated.
Morrison Formation: A Late Jurassic geological formation in western North America known for abundant dinosaur fossils. Its dinosaur remains include stones historically interpreted as gastroliths.
Convergent evolution: The independent evolution of similar traits in unrelated lineages facing comparable conditions. Similar stone-swallowing behavior may have evolved independently in different animal groups.
Crop (anatomy): An expandable pouch in the esophagus of some animals that temporarily stores food. In birds, food may be held in the crop before reaching the gizzard and its stones.
Sauropod: A group of long-necked, herbivorous dinosaurs that includes the largest land animals known. Some sauropod fossils are associated with stones interpreted as possible gastroliths.