''Pisidium'' is a
genus of very small or minute
freshwater clam
Freshwater bivalves are one kind of freshwater mollusc, along with freshwater snails. They are bivalves that live in fresh water as opposed to salt water, which is the main habitat type for bivalves.
The majority of species of bivalve molluscs l ...
s known as pill clams or pea clams,
aquatic bivalve
Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...
mollusc
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...
s 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 eggshell
An eggshell is the outer covering of a hard-shelled egg and of some forms of eggs with soft outer coats.
Diversity
Worm eggs
Nematode eggs present a two layered structure: an external vitellin layer made of chitin that confers mechanical ...
s are rare.
This is because the breakdown of
tannins from the local
coniferous
Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All extant ...
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.
The slow dissolution of these minute bivalve shells released
calcium carbonate into the water, raising the water's
pH high enough that it prevented the hadrosaur eggshell fragments from dissolving before they could be fossilized.
Extant subgenera and species
Extant subgenera and species within the genus ''Pisidium'' include:
Subgenus ''Euglesa'' Jenyns, 1832
*''
Pisidium casertanum'' (Poli, 1791)
*''
Pisidium globulare'' Clessin, 1873
*''
Pisidium personatum'' Malm, 1855
Subgenus ''Pisidium''
Pfeiffer, 1821
*''
Pisidium amnicum'' (O. F. Müller, 1774)
*''
Pisidium dilatatum'' Westerlund, 1897
Subgenus ''Cyclocalyx''
Dall, 1903
*''
Pisidium hinzi
''Euglesa hinzi'' is a species of mollusc belonging to the family Sphaeriidae.
It is native to Northern Europe.
Synonym:
* ''Pisidium hinzi'' Kuiper, 1975 (= basionym
In the scientific name of organisms, basionym or basyonym means the original ...
'' Kuiper, 1975
*''
Pisidium obtusale'' (
Lamarck, 1818)
Subgenus ''Tropidocyclas''
Dall, 1903
*''
Pisidium henslowanum'' (Sheppard, 1823)
*''
Pisidium lilljeborgii'' Clessin, 1886
*''
Pisidium supinum'' A. Schmidt, 1851
*''
Pisidium waldeni
''Euglesa waldeni'' is a species of mollusc belonging to the family Sphaeriidae.
It is native to Northern Europe.
Synonym:
* ''Pisidium waldeni'' Kuiper, 1975 (= basionym
In the scientific name of organisms, basionym or basyonym means the orig ...
'' Kuiper, 1975
Subgenus ''Hiberneuglesa'' Starobogatov, 1983
*''
Pisidium hibernicum'' Westerlund, 1894
Subgenus ''Cingulipisidium'' Pirogov & Starobogatov, 1974
*''
Pisidium crassum''
Stelfox, 1918
*''
Pisidium milium
''Pisidium milium'' is a species of very small freshwater bivalve in the family Sphaeriidae, the fingernail clams and pea clams.
Description
The 3.0- to 4.5-mm shell is tumid (swollen). It is more rectangular than other ''Pisidium'' specie ...
'' Held, 1836
*''
Pisidium nitidum
''Pisidium nitidum'', the shining pea clam, is a species of minute freshwater clam, an aquatic bivalve mollusc in the family Sphaeriidae, the pea clams and fingernail clams.
Description
The 3 – 4 mm. shell is slightly tumid (swollen). ...
'' Jenyns, 1832
*''
Pisidium pseudosphaerium'' Favre, 1927
Subgenus ''Pseudeupera'' Germain, 1909
*''
Pisidium pulchellum
''Pisidium pulchellum'' , the iridescent pea mussel, is a minute species of pea clam, a freshwater bivalve in the family Sphaeriidae.
Description
The 3.5–4 mm shell is tumid (swollen), oblique-oval shell. The umbos are broad well and w ...
'' Jenyns, 1832
*''
Pisidium subtruncatum'' Malm, 1855
Subgenus ''Neopisidium''
Odhner, 1921
*''
Pisidium conventus
''Pisidium conventus'', the arctic-alpine pea clam, is a species of freshwater bivalve from the family Sphaeriidae.
Description
The small (2.2–2.8 mm.) shell is oval in shape and thin and fragile. It is broad and flattened (laterally com ...
'' Clessin, 1867
Subgenus ''Odhneripisidium'' Kuiper, 1962
*''
Pisidium moitessierianum'' Paladilhe, 1866
*''
Pisidium tenuilineatum
''Pisidium tenuilineatum'', the fine-lined pea mussel, is a species of very small freshwater bivalve in the family Sphaeriidae.
Distribution
The species is native to Europe.
* British Isles – listed in List of endangered species in the Britis ...
''
Stelfox, 1918
Subgenus ''Afropisidium'' Kuiper, 1962
*''
Pisidium giraudi'' Bourguignat, 1885
*''
Pisidium hodgkini
''Pisidium hodgkini'' is a freshwater bivalve of the family Sphaeriidae, which is found in New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North ...
'' (
Suter
Suter is a surname. Notable people with the name include:
* Alexis P. Suter (born 1963), American blues, and soul blues singer and songwriter
* Andrew Burn Suter (1830–1895), Bishop of the Diocese of Nelson, New Zealand
* August Suter (1887& ...
, 1905)
*''
Pisidium pirothi
''Afropisidium pirothi'' is a species of bivalve belonging to the family Sphaeriidae.
The species is found in Africa.
References
Sphaeriidae
Bivalves described in 1881
Bivalves of Africa
{{Sphaeriidae-stub ...
'' Jickeli, 1881
Subgenus unknown
*''
Pisidium artifex
''Pisidium artifex'' is a species of freshwater clam in the family Sphaeriidae. It is endemic to Kenya, where it is known only from Mount Kenya
Mount Kenya (Kikuyu: ''Kĩrĩnyaga'', Kamba, ''Ki Nyaa'') is the highest mountain in Kenya and t ...
'' Kuiper, 1960
*''
Pisidium stewarti'' Preston, 1909
Subgenus '
*''
Pisidium annandalei
''Pisidium'' is a genera, genus of very small or minute freshwater clams known as pill clams or pea clams, Aquatic animal, aquatic bivalve molluscs in the family (biology), family Sphaeriidae, the pea clams and fingernail clams.
In some bivalv ...
'' Prashad, 1925
*''
Pisidium edlaueri
''Pisidium'' is a genus of very small or minute freshwater clams known as pill clams or pea clams, aquatic bivalve molluscs in the family Sphaeriidae, the pea clams and fingernail clams.
In some bivalve classification systems, the family Spha ...
'' Kuiper, 1960
*''
Pisidium javanum''
van Benthem Jutting, 1931
*''
Pisidium maasseni
''Euglesa maasseni'' is a species of bivalve belonging to the family Sphaeriidae
Sphaeriidae is a family of small to minute freshwater bivalve molluscs in the order Sphaeriida. In the US, they are commonly known as pea clams or fingernail cl ...
'' Kuiper, 1987
*''
Pisidium punctiferum
''Pisidium punctiferum'', the striate peaclam, is a freshwater bivalve of the family (biology), family Sphaeriidae.
Distribution
The type locality is a pond at Saint Ann's River, Trinidad and Tobago, Saint Ann's River, near Port of Spain, Tri ...
'' (Guppy, 1867)
*''
Pisidium raddei
''Pisidium'' is a genus of very small or minute freshwater clams known as pill clams or pea clams, aquatic bivalve molluscs in the family Sphaeriidae, the pea clams and fingernail clams.
In some bivalve classification systems, the family Spha ...
'' Dybowski, 1902
* 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
References
* 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
''Pisidium''keyed, described and illustrated in ''Danmarks Fauna'' (Georg Mandahl-Barth)
''Pisidium'' imagesat
Consortium for the Barcode of Life
* https://web.archive.org/web/20141128091542/http://sunsite.ualberta.ca/Projects/Aquatic_Invertebrates/?Page=20
{{Taxonbar, from=Q600521
Bivalve genera