Atrina is a cosmopolitan genus of bivalve molluscs belonging to the family Pinnidae.

Temporal range: Triassic - Recent
Horse mussel, Atrina zelandica.jpg
Atrina zelandica
Pinnidae - Atrina pectinata.JPG
Fossil of Atrina pectinata
Scientific classification e
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Pteriida
Family: Pinnidae
Genus: Atrina
Gray, 1847

A typical species is A. fragilis, found in British waters. A. rigida (Lightfoot, 1786) is found on the southeast coast of North America and in the West Indies. The type species is A. nigra (Dillwyn, 1817, originally P. nigra).

Atrina is considered to represent the more primitive form within the Pinnidae; however, both genera Pinna and Atrina are very ancient. The genus Atrina is represented within the fossil record from the Triassic period to the Quaternary period (age range: 242.0 to 0.0 million years ago). These fossils have been found all over the world.[1]


Molluscs within this genus are characterized by elongated, wedge-shaped shells, distinguished from the genus Pinna by the lack of any grooves in the nacreous lining of the shell, and by the central positioning of the adductor scar.

As with other pen shells (Pinnidae) they commonly stand point-first in the sea bottom in which they live, anchored by net of byssus threads.


Species within the genus Atrina include:[1]


  • Packard, Earl; Jones, David L. (Sep 1965). "Cretaceous Pelecypods of the Genus Pinna from the West Coast of North America". Journal of Paleontology. 39 (1): 910–915.
  • "Glossary". Man and Mollusc. Archived from the original on 18 January 2008. Retrieved 2008-01-30.
  • Mitchell, Patricia B. "American Stiff Pen Shell: Strength and Rigidity". Archived from the original on 20 December 2007. Retrieved 2008-01-31.

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