Gastrolith
A gastrolith, also called a stomach stone or gizzard stone, is a
Etymology
Gastrolith comes from the
Occurrence
Among living
Some
Certain crayfish store gastroliths in their stomachs. Crayfish living in freshwater store these gastroliths as the presence of calcium is limited in freshwater. These gastroliths serve as a calcium source for molting.[4][5][6]
Paleontology
History of discovery
In 1906,
Identification
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 rilles, presumably caused by contact with stomach acid. 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.
None of the gastroliths examined in a 2001 study of Cedarosaurus gastroliths had the "soapy" texture popularly used to distinguish gastroliths from other types of clast.[10] The researchers dismissed using a soapy texture to identify gastroliths as "unreliable".[10] Gastroliths tended to be universally dull, although the colors represented were varied including black, dark brown, purplish red and grey-blue.[10] Reflectance values greater than 50% are very diagnostic for identifying gastroliths.[10] Clasts from beaches and streams tended to have reflectance values of less than 35%.[11] Less than ten percent of beach clasts have reflectance values lying between 50 and 80%.[12]
, about midway between shoulder and pelvis.Geologic distribution
Jurassic
Gastroliths have sometimes been called Morrison stones because they are often found in the
Cretaceous
The Early Cretaceous Cedar Mountain Formation of Central Utah is full of highly polished red and black cherts, and other rounded quartzose clasts, which may partly represent gastroliths. 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.
Sauropods
Most known instances of preserved
Cedarosaurus weiskopfae
In 2001 Frank Sanders, Kim Manley, and Kenneth Carpenter published a study on 115 gastroliths discovered in association with a Cedarosaurus specimen.[15] The stones were identified as gastroliths on the basis of their tight spatial distribution, partial matrix support, and an edge-on orientation indicative of their being deposited while the carcass still had soft tissue.[15] Their high surface reflectance values are consistent with other known dinosaur gastroliths.[15] Nearly all of the Cedarosaurus gastroliths were found within a .06 m volume[clarification needed] of space in the gut region of the skeleton.[16]
The total mass of the gastroliths themselves was 7 kilograms (15 lb).[17] Most were less than 10 millilitres (0.35 imp fl oz; 0.34 US fl oz) in volume.[18] The least massive clast was 0.1 grams (0.0035 oz) and the most was 715 grams (25.2 oz), with most of them being toward the smaller end of that range.[18] The clasts tended to be close to spherical in shape, although the largest specimens were also the most irregular.[18] The largest gastroliths contributed the most to the total surface area of the set.[19] Some gastroliths were so large and irregularly shaped that they may have been difficult to swallow.[19] The gastroliths were mostly composed of chert, with some sandstone, siltstone, and quartzite clasts also included.[10]
Since some of the most irregular gastroliths are also the largest, it is unlikely that they were ingested by accident.[19] Cedarosaurus may have found irregular clasts to be attractive potential gastroliths or was not selective about shape.[19] The clasts were generally of dull coloration, suggesting that color was not a major factor for the sauropod's decision making.[15] The high surface area to volume ratio of the largest clasts suggests that the gastroliths may have broken down ingested plant material by grinding or crushing it.[12] The sandstone clasts tended to be fragile and some broke in the process of collection.[10] The sandstone gastroliths may have been rendered fragile after deposition by loss of cement caused by the external chemical environment.[20] If the clasts had been that fragile while the animal was alive, they probably rolled and tumbled in the digestive tract.[12] If they were more robust, they could have served as part of a ball-mill system.[12]
Migration
See also
Footnotes
- ^ a b Rondeau, et al Larval Anurans Adjust Buoyancy in Response to Substrate Ingestion Copeia: February 2005, Vol. 2005, No. 1, pp. 188-195.
- ^ Wickramasinghe, DD et al Ontogenetic changes in diet and intestinal morphology in semi-terrestrial tadpoles of Nannophrys ceylonensis (Dicroglossidae) Copeia, Vol2007, Iss 4 (Dec 2007)
- ^ Darby and Ojakangas (1980).
- ^ "Crayfish Gastroliths". to know the land.
- S2CID 26280256.
- ^ "Why freshwater crayfish don't need milk for healthy bones | Western Australian Museum". museum.wa.gov.au.
- ^ Wieland, G. R., 1906, Dinosaurian gastroliths: Science, v. 23, p. 819-821.
- ^ Brown, B. 1907. Gastroliths. Science 25(636): 392.
- ^ Huene, F. von. 1932. Die fossile Reptil-Ordnung Saurischia, ihre Entwicklung und Geschichte. Monographien für Geologie und Paläontologie (1) 4: 1–361.
- ^ a b c d e f "Description," Sanders et al. (2001). Page 176.
- ^ "Description," Sanders et al. (2001). Pp. 176-177.
- ^ a b c d "Description," Sanders et al. (2001). Page 177.
- ^ a b "Occurrence of Gastroliths in Mesozoic Taxa," Sanders et al. (2001). Page 168.
- ISBN 1-4051-3413-5.
- ^ a b c d "Abstract," Sanders et al. (2001). Page 166.
- ^ "Occurrence in Cedarosaurus," Sanders et al. (2001). Page 169.
- ^ "Table 12.2," Sanders et al. (2001). Page 171.
- ^ a b c "Description," Sanders et al. (2001). Page 172.
- ^ a b c d "Description," Sanders et al. (2001). Page 174.
- ^ "Conclusion," Sanders et al. (2001). Page 177.
References
- Darby, D.G. and Ojakangas, J. (1980). Gastroliths from an Upper Cretaceous Plesiosaur. Journal of Paleontology 54:3
- 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. Martin (April 2007). "No gastric mill in sauropod dinosaurs: new evidence from analysis of gastrolith mass and function in ostriches". PMID 17254987.
- Stokes, W. L. 1987. Dinosaur gastroliths revisited. Journal of Paleontology 61: 1242–1246.
- Sanders, F.; Manley, K.; Carpenter, K. (2001). "Gastroliths from the Lower Cretaceous sauropod Cedarosaurus weiskopfae". In Tanke, Darren; Carpenter, Ken (eds.). Mesozoic Vertebrate Life: New Research Inspired by the Paleontology of Philip J. Currie. Indiana University Press. pp. 166–180. ISBN 0-253-33907-3.
- Schmeisser, R.L. and Gilette, D.D. (2009). Unusual occurrence of gastroliths in a polycotylid plesiosaur from the Upper Cretaceous Tropic Shale, southern Utah. "PALAIOS",24(7):453-459. [1]