Pisidium is a genera of very small or minute known as pill clams or pea clams, Aquatic animal bivalve in the family Sphaeriidae, the pea clams and fingernail clams.
In some bivalve classification systems, the family Sphaeriidae is referred to as Pisidiidae, and occasionally Pisidium species are grouped in a subfamily known as Pisidiinae.
Pisidium and taphonomy
In large enough quantities, the minute shells of these bivalves can affect environmental conditions, and this change in conditions can positively affect the ability of organic remains in the immediate environment to fossilize (one aspect of
taphonomy).
For example, in the Dinosaur Park Formation, the fossil remains of
hadrosaur are rare.
This is because the breakdown of
from the local
coniferous vegetation caused the ancient waters to be acidic, and therefore usually eggshell fragments dissolved in the water before they had a chance to be fossilized.
Hadrosaur eggshell fragments are however present in two microfossil sites in the area. Both of these sites are dominated by preserved shells of invertebrate life, primarily shells of pisidiids.
Extant subgenera and species
Extant subgenera and species within the genus
Pisidium include:
Subgenus Euglesa Jenyns, 1832
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Pisidium casertanum (Poli, 1791)
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Pisidium globulare Clessin, 1873
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Pisidium personatum Malm, 1855
Subgenus Pisidium Pfeiffer, 1821
Subgenus Cyclocalyx Dall, 1903
Subgenus Tropidocyclas Dall, 1903
Subgenus Hiberneuglesa Starobogatov, 1983
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Pisidium hibernicum Westerlund, 1894
Subgenus Cingulipisidium Pirogov & Starobogatov, 1974
Subgenus Pseudeupera Germain, 1909
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Pisidium pulchellum Jenyns, 1832
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Pisidium subtruncatum Malm, 1855
Subgenus Neopisidium Odhner, 1921
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Pisidium conventus Clessin, 1867
Subgenus Odhneripisidium Kuiper, 1962
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Pisidium moitessierianum Paladilhe, 1866
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Pisidium tenuilineatum Stelfox, 1918
Subgenus Afropisidium Kuiper, 1962
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Pisidium giraudi Bourguignat, 1885
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Pisidium hodgkini (Henry Suter, 1905)
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Pisidium pirothi Jickeli, 1881
[Appleton C., Ghamizi M., Jørgensen A., Kristensen T. K., Lange C., Stensgaard A-S. & Van Damme D. (2009). Pisidium pirothi. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. . Downloaded on 3 December 2010.]
Subgenus unknown
Subgenus incertae sedis
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Pisidium annandalei Prashad, 1925
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Pisidium edlaueri Kuiper, 1960
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Pisidium javanum van Benthem Jutting, 1931
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Pisidium maasseni Kuiper, 1987
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Pisidium punctiferum (Guppy, 1867)
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Pisidium raddei Dybowski, 1902
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undescribed Pisidium species from Africa (Kuiper, in prep., awaiting additional records)
[Kuiper J.G.J. (2009). "Fossil records of Palaearctic Pisidium species in tropical Africa". Zoologische Mededelingen 83(10): 593-594. HTM .]
Footnotes
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Tanke, D.H. and Brett-Surman, M.K. 2001. Evidence of Hatchling and Nestling-Size Hadrosaurs (Reptilia:Ornithischia) from Dinosaur Provincial Park (Dinosaur Park Formation: Campanian), Alberta, Canada. pp. 206–218. In: Mesozoic Vertebrate Life—New Research Inspired by the Paleontology of Philip J. Currie. Edited by D.H. Tanke and K. Carpenter. Indiana University Press: Bloomington. xviii + 577 pp.
External links
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Pisidium keyed, described and illustrated in Danmarks Fauna (Georg Mandahl-Barth)
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Pisidium images at Consortium for the Barcode of Life
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