Pisidium

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Pisidium
Pisidium pseudosphaerium.png
External view of the left valve of Pisidium pseudosphaerium
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Sphaeriida
Superfamily: Sphaerioidea
Family: Sphaeriidae
Genus: Pisidium
C. Pfeiffer, 1821
Type species
Pisidium amnicum
(O. F. Müller, 1774)
Species

See text

Synonyms [1]
List
    • Pisidium (Pisidium) C. Pfeiffer, 1821
    • Corneocyclas (Pisidium) C. Pfeiffer, 1821
    • Cyclas (Pisidium) C. Pfeiffer, 1821
    • Cyrena (Pisidium) C. Pfeiffer, 1821
    • Pera Leach, 1831
    • Cordula Leach, 1852
    • Pisidium (Fluminina) Clessin, 1873
    • Amniciana Servain, 1888
    • Pisidium (Amniciana) Servain, 1888
    • Lacustrina Sterki, 1916
    • Pisidium (Lacustrina) Sterki, 1916
    • Pisidium (Parapisidium) Kuiper, 1966
    • Pisidium (Amuropisidium) Prozorova, 1995

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.

Contents

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.

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). [2] For example, in the Dinosaur Park Formation, the fossil remains of hadrosaur eggshells are rare. [3] This is because the breakdown of tannins 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. [4]

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. [3] 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. [5]

Extant subgenera and species

Extant species within the genus Pisidium include: [1]

The following species require evaluation to confirm their placement in Pisidium; many of the following are taxa inquirenda and have not been used by recent authors: [1]

The genera Conventus , Euglesa , Hindupisidium , Odhneripisidium , and Sphaerium were split out from Pisidium after taxonomic revision. [1]

Footnotes

  1. 1 2 3 4 Bieler R, Bouchet P, Gofas S, Marshall B, Rosenberg G, La Perna R, Neubauer TA, Sartori AF, Schneider S, Vos C, ter Poorten JJ, Taylor J, Dijkstra H, Finn J, Bank R, Neubert E, Moretzsohn F, Faber M, Houart R, Picton B, Garcia-Alvarez O (eds.). "Pisidium C. Pfeiffer, 1821". MolluscaBase. World Register of Marine Species . Retrieved 11 February 2026.
  2. ↑ Tanke and Brett-Surman (2001).
  3. 1 2 "Abstract," Tanke and Brett-Surman (2001). Page 206.
  4. ↑ "Discussion," Tanke and Brett-Surman (2001). Page 212.
  5. ↑ "Eggshell," Tanke and Brett-Surman (2001). Page 209.
  6. ↑ Kuiper J.G.J. (2009). "Fossil records of Palaearctic Pisidium species in tropical Africa". Zoologische Mededelingen 83(10): 593-594. HTM Archived 4 March 2016 at the Wayback Machine .

References

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