Exogyra Explained

Exogyra is an extinct genus of fossil marine oysters in the family Gryphaeidae, the foam oysters or honeycomb oysters.^[1] These bivalves were cemented by the more cupped left valve. The right valve is flatter, and the beak is curved to one side. Exogyra lived on solid substrates in warm seas during the Jurassic and Cretaceous periods.

Taxonomy

The former subgenus Exogyra (Aetostreon) Bayle, 1878,^[2] is sometimes considered a separate genus due to a lack of the fine set of parallel ribs (chomata) separated by pits on the inner surface of the valves (which is present in the nominate subgenus).^[3]

Distribution

Fossils of Exogyra have been found in:^[4]

JurassicAfghanistan, Chile, China, Eritrea, Ethiopia, France, Germany, India, Kenya, Poland, Portugal, Somalia, Spain, Tanzania, the United Kingdom, and Yemen.

CretaceousAfghanistan, Algeria, Argentina, Brazil, Bolivia, Canada (British Columbia), Bulgaria, Chile, Colombia (Hiló Formation, Tolima, Macanal and Chipaque Formations, Eastern Ranges),^{[5] [6]} Cuba, the Czech Republic, Egypt, Ethiopia, France, Germany, Greenland, Hungary, India, Iran, Israel, Italy, Jordan, Lebanon, Libya, Madagascar, Mexico, Morocco, Mozambique, New Zealand, Nigeria, Oman, Pakistan, Peru, Poland, Portugal, Serbia and Montenegro, Slovakia, South Africa, Spain, Sweden, Switzerland, Tanzania, Trinidad and Tobago, Tunisia, Turkey, USSR, Ukraine, the United Kingdom, United States (Alabama, Arizona, Arkansas, California, Colorado, Delaware, Georgia, Maryland, Minnesota, Mississippi, Missouri, Montana, New Jersey, New Mexico, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Utah, Wyoming), Venezuela, and Yemen.

References

Bibliography

Further reading

• National Audubon Society Field Guide to North American Fossils

Notes and References

1. Web site: Evolution of Exogyra plexa . 25 March 2008 . https://web.archive.org/web/20080326192109/http://crnmac1.physics.uiowa.edu/fossils/oysters/ilymatogyra/Exogyra-plexa.html . 26 March 2008 . dead .
2. Web site: †Exogyra (Aetostreon) Bayle 1878 . Paleobiology Database . Fossilworks . 17 December 2021 . 13 December 2021 . https://web.archive.org/web/20211213054834/http://www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=118251 . dead .
3. Pugaczewska . Halina . 1975 . Neocomian oysters from Central Poland . Acta Palaeontologica Polonica . 20 . 1 . 47–72 .
4. http://www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=16655 Exogyra
5. Piraquive et al., 2011, p. 204
6. Acosta & Ulloa, 2002, p. 54