Gastroliths ('stomach stones' or 'gizzard stones') are rocks, which are or have been held inside the digestive tract of an animal. Among living vertebrates, gastroliths are common among herbivorous birds, crocodiles, alligators, seals and sea lions. Domestic fowl, for instance, require access to 'grit', for the purpose of food-grinding. Gastroliths are retained in the very muscular gizzard and serve the masticatory function of teeth, in an animal without suitable grinding teeth. The grain size of the gastrolith depends upon the size of the animal and its special needs. Particles as small as sand and stones the size of cobbles or greater have been found. In anatomy, the stomach is a bean-shaped hollow muscular organ of the gastrointestinal tract involved in the second phase of digestion, following mastication. ... The gizzard is an adapted stomach that is found in birds, earthworms, and other animals. ... This balancing rock, Steamboat Rock stands in Garden of the Gods park in Colorado Springs, CO The rocky side of a mountain creek near Orosí, Costa Rica. ... A fowl is a bird of any kind, although some types of birds use the word specifically in their names (for example, Guineafowl and Peafowl). ... Types of teeth Molars are used for grinding up foods Carnassials are used for slicing food. ... This article deals with grain size in the context of geology, see crystallite for grain size in materials science. ... For other uses, see Sand (disambiguation). ... Cobble is a geologic term for a rock or rock fragment with a grain size with dimensions between 64–256 mm (2. ...

Some extinct animals, such as sauropod dinosaurs, appear to have used stones to grind tough plant matter. Gastroliths have only rarely been found in association with fossils of theropod dinosaurs and a trituration of their food with the stones is not plausible. Aquatic animals, such as plesiosaurs, may have used them as ballast, to help balance themselves or to decrease their buoyancy, as crocodiles do. More research is needed, to understand the function of the stones in aquatic animals. While some fossil gastroliths are rounded and polished, many stones in living birds are not polished at all. Gastroliths associated with dinosaur fossils can be several kilograms in weight. Stones swallowed by ostriches can also reach a length of more than 10 cm. Trituration is the grinding of powders in a mortar with a pestle. ... Genera Crocodylus Osteolaemus Tomistoma A crocodile can be any of the 14 species of large, water-loving reptiles in the family Crocodylidae (sometimes classified instead as the subfamily Crocodylinae). ... Orders & Suborders Saurischia Sauropodomorpha Theropoda Ornithischia Thyreophora Ornithopoda Marginocephalia Dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for over 160 million years, first appearing approximately 230 million years ago. ...

Geologists usually require several pieces of evidence before they will accept that a rock was used by a dinosaur to aid its digestion. First, the stone must be unlike the rock found in its geological vicinity. Secondly, it should be rounded and polished, because inside a dinosaur's gizzard any genuine gastrolith would have been acted upon by other stones and fibrous materials in a process similar to the action of a rock tumbler. Lastly, the stone must be found with the bones of the dinosaur which ingested it. It is this last criterion that causes trouble in identification, as smooth stones found without context can (possibly erroneously in some cases) be dismissed as having been polished by water or wind. Whittle (1988,9) pioneered scanning electron microscope analysis of wear patterns on gastroliths. Wings (2003) found that ostrich gastroliths would be deposited outside the skeleton if the carcass was deposited in an aquatic environment for as little as a few days following death. He concludes that this is likely to hold true for all birds (with the possible exception of moa) due to their air-filled bones which would cause a carcass deposited in water to float for the time it needs to rot sufficiently to allow gastrolith escape. The Geologist by Carl Spitzweg A geologist is a contributor to the science of geology, studying the physical structure and processes of the Earth and planets of the solar system (see planetary geology). ... This article does not cite any references or sources. ... Tumble polishing, or tumbling, is a technique for smoothing and polishing a hard substance. ... Grays Anatomy illustration of a human femur. ... Binomial name Carolus Linnaeus, 1758 The present-day distribution of Ostriches. ... Look up aquatic in Wiktionary, the free dictionary. ... Genera Anomalopteryx (bush moa) Euryapteryx Megalapteryx (upland moa) Dinornis (giant moa) Emeus Pachyornis Moa were giant flightless birds native to New Zealand. ...

Gastroliths can be distinguished from stream- or beach-rounded rocks by several criteria: gastroliths are highly polished on the higher surfaces, with little or no polish in depressions or crevices, often strongly resembling the surface of worn animal teeth. Stream- or beach-worn rocks, particularly in a high-impact environment, show less polishing on higher surfaces, often with many small pits or cracks on these higher surfaces. Finally, highly polished gastroliths often show long microscopic hairline scratches, presumably caused by contact with a sharp corner of a freshly swallowed stone. Since most gastroliths were scattered when the animal died and many entered a stream or beach environment, some gastroliths show a mixture of these wear features. Others were undoubtedly swallowed by other dinosaurs and highly polished gastroliths may have been swallowed repeatedly.

The American Museum of Natural History Photograph # 311488 demonstrates an articulated skeleton of a Protiguanadon mongoliense, from the Ondai Sair Formation, Lower Cretaceous Period of Mongolia, showing a collection of about 40 gastroliths inside the rib cage, about midway between shoulder and pelvis. // The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i. ... A geologic period is a subdivision of geologic time that divides an era into smaller timeframes. ...

The Early Cretaceous Cedar Mountain Formation of Central Utah is full of highly polished red and black cherts, which may partly represent gastroliths. Interestingly, the cherts may themselves contain fossils of ancient animals, such as corals. These stones do not appear to be associated with stream deposits and are rarely more than fist-sized, which is consistent with the idea that they are gastroliths. Gastroliths have sometimes been called 'Morrison stones' because they are often found in the Morrison Formation (named after the town of Morrison, west of Denver, Colorado), a late Jurassic formation roughly 150 million years old. Some gastroliths are made of petrified wood. The Cedar Mountain Formation is the name given to distinctive sedimentary rocks in eastern Utah that occur between the underlying Morrison Formation and overlying Naturita Formation (sometimes incorrectly called the Dakota Formation). ... This article is about the U.S. state. ... Chert Chert (IPA: ) is a fine-grained silica-rich cryptocrystalline sedimentary rock that may contain small fossils. ... The Morrison Formation is a distinctive body of rock in the western United States and Canada that has been the most fertile source of fossils in North America. ... Morrison is a town in Jefferson County, Colorado, in the United States. ... This article refers to the state capital of Colorado. ... Official language(s) English Capital Denver Largest city Denver Largest metro area Denver-Aurora Metro Area Area  Ranked 8th  - Total 104,185 sq mi (269,837 km²)  - Width 280 miles (451 km)  - Length 380 miles (612 km)  - % water 0. ... The Jurassic Period is a major unit of the geologic timescale that extends from about 199. ...

Paleontologists are researching new methods of identifying gastroliths that have been found disassociated from animal remains, because of the important information they can provide. If the validity of such gastroliths can be verified, it may be possible to trace gastrolithic rocks back to their original sources. This may provide important information on how dinosaurs migrated. Because the number of suspected gastroliths is large, they could provide significant new insights into the lives and behavior of dinosaurs. A paleontologist carefully chips rock from a column of dinosaur vertebrae. ... mtDNA-based chart of large human migrations. ...

See also

• Regurgitalith
• Coprolite

Regurgitaliths[1][2] are the fossilised remains of contents that has been regurgitated by an animal. ... Coprolites are fossilized feces, or animal dung. ...

References

Whittle, C. (1989). On the Origins of Gastroliths: Determining the Weathering Environment of Rounded and Polished Stones by Scanning Electron Microscope Analysis. Geological Society of America Bulletin 51:5.

Whittle, C. (1988). On the Origins of Gastroliths. Journal of Vertebrate Paleontology, Supplement to 3:28.

• Wings, Oliver (2003): Observations on the Release of Gastroliths from Ostrich Chick Carcasses in Terrestrial and Aquatic Environments. Journal of Taphonomy 1(2): 97-103. PDF fulltext

• Wings, Oliver (2004): Identification, distribution, and function of gastroliths in dinosaurs and extant birds with emphasis on ostriches (Struthio camelus). Ph.D. Thesis, The University of Bonn, Bonn, Germany, 187 pp. URN: urn:nbn:de:hbz:5N-04626 PDF fulltext

• Wings, Oliver (2007): A review of gastrolith function with implications for fossil vertebrates and a revised classification. Acta Palaeontologica Polonica 52(1): 1-16. PDF fulltext

• Wings, Oliver & Sander, P.M. (2007): No gastric mill in sauropod dinosaurs: new evidence from analysis of gastrolith mass and function in ostriches. Proc. R. Soc. B 274(1610): 635–640. doi:10.1098/rspb.2006.3763 PDF fulltext