Exogyra

Exogyra is an extinct genus of fossil marine oysters in the family Gryphaeidae, the foam oysters or honeycomb oysters.[1] These bivalves grew 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.

Exogyra
Temporal range: Jurassic-Cretaceous
Exogyra flabellata
(Owl Creek Formation, Late Cretaceous, Mississippi)
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Ostreida
Family: Gryphaeidae
Genus: †Exogyra
Species

See text

The subgenus Aetostreon 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).[2]

Species
Exogyra costata, Prairie Bluff Chalk Formation (Maastrichtian); Starkville, Mississippi
Exogyra (subgenus Exogyra) (Say, 1820)
  • Exogyra africana Say, 1820[3]
  • Exogyra aquillana Stephenson, 1953
  • Exogyra arietina[4][5]
  • Exogyra callophyla Ihering, 1903
  • Exogyra cancellata Stephenson, 1914
  • Exogyra clarki Shattuck, 1903
  • Exogyra columbella Meek, 1876
  • Exogyra contorta Eichwald, 1868
  • Exogyra costata
  • Exogyra davidsoni[6]
  • Exogyra columba
  • Exogyra erraticostata Stephenson[7]
  • Exogyra fimbriata Conrad, 1855
  • Exogyra flabellata
  • Exogyra ganhamoroba Maury, 1936
  • Exogyra guadalupae Whitney, 1937 (thesis)
  • Exogyra haliotoidea Maury, 1936
  • Exogyra laevigata[8]
  • Exogyra laeviuscula Roemer, 1849
  • Exogyra lancha Stoyanow, 1949
  • Exogyra levis Stephenson, 1952
  • Exogyra mutatoria White, 1887
  • Exogyra obliquata Pulteney[9]
  • Exogyra paupercula Cragin, 1893
  • Exogyra plexa Cragin, 1893
  • Exogyra potosina Castillo and Aguilera, 1895
  • Exogyra ponderosa Roemer, 1852
  • Exogyra praevirgula Douville & Jourdy, 1924[10][11]
  • Exogyra quitmanensis Cragin, 1893
  • Exogyra sergipensis Maury, 1936
  • Exogyra sigmoidea Reuss, 1844[12]
  • Exogyra solea Muller, 1910
  • Exogyra upatoiensis Stephenson, 1914
  • Exogyra whitneyi Bose, 1910
  • Exogyra woolmani Richards, 1947

Exogyra (subgenus Aetostreon) (Bayle, 1878)[13]

  • Exogyra aquila Brongniart, 1871
  • Exogyra bale
  • Exogyra couloni Say, 1820
  • Exogyra imbricatum (possibly a morphotype of E. couloni) Kraus, 1843[2]
  • Exogyra latissimum[14]
  • Exogyra miotaurinensis Sacco, 1897[15] (Type species of subgenus)
  • Exogyra neocomiensis[16]
  • Exogyra pilmatuegrossum[17]
  • Exogyra rectangularis[16]

Distribution

Fossils of Exogyra have been found in:[18]

Jurassic

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

Cretaceous

Afghanistan, Algeria, Argentina, Brazil,Bolivia,Canada (British Columbia), Chile, Colombia (Hiló Formation, Tolima, Macanal and Chipaque Formations, Eastern Ranges),[19][20] Cuba, the Czech Republic, Egypt, Ethiopia, France, Germany, Greenland, Hungary, India, Iran, 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.

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References
  1. "Evolution of Exogyra plexa". Archived from the original on 26 March 2008. Retrieved 25 March 2008.
  2. Pewgaczewska.H.
  3. Exogyra africana
  4. "Bivalve Fossil Record curriculum" (PDF). Archived from the original (PDF) on 6 November 2014. Retrieved 5 November 2014.
  5. "Catalog number 528130". Archived from the original on 5 November 2014. Retrieved 5 November 2014.
  6. Exogyra davidsoni at Fossilworks.org
  7. Exogyra
  8. Lake.P., and Rastall.R.H., (1913), A Text Book of Geology, 2nd edition, London: Edward Arnold's Geological series Page 426 and 436
  9. Castell. C.P., and Cox. L.R., (1975), British Mesozoic Fossils, 5th edition, London: Trustees of the British Museum (Natural History), page 86
  10. Exogyra praevirgula
  11. Global Names Index
  12. Ivanov. M., Hrdlickova. S., and Gregorova. R., (2005), The Complete Encyclopedia of Fossils, 3rd. ed., Lisse: Rebo International, page 133
  13. Paleobiology Database, Exogyra (Aetostreon), accessed 7 May 2013
  14. Anon, Aetostreon latissium As a Derived Fossil, accessed 7 May 2013
  15. Paleobiology Database, Exogyra (Aetostreon miotaurinensis), accessed 7 May 2013
  16. Global Names Index, (2000), Global Names Index, accessed 7 May 2013
  17. Rubillar, A.E; Lazo, E.B. (2008). "Description of Aetostreon pilmatuegrossum sp. Nov. from the Lower Cretaceous of Argentina (Neuquén Basin), and significance of the conservative left valve morphology in oysters of the genus Aetostreon Bayle". Cretaceous Research. 30 (3): 727–748. doi:10.1016/j.cretres.2008.12.013.
  18. Exogyra at Fossilworks.org
  19. Piraquive et al., 2011, p.204
  20. Acosta & Ulloa, 2002, p.54

Bibliography

Further reading
  • National Audubon Society Field Guide to North American Fossils


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