Species Account

Atrina fragilis (Pennant, 1777)

Pinnoidea : Pinnidae

Tebble name: Pinna fragilis Pennant
Smith & Heppell name: Atrina fragilis (Pennant, 1777)

To size: To 480mm. Shell Structure: Thin but strong, horny. Equivalve: Equivalve. Equilateral: Strongly inequilateral, beaks at the anterior end. Outline: Triangular, dorsal margin long and straight, posterior broad, gently curved but often damaged; ventral margin slightly sinuous. Contour: Posterior margins gape; small byssus gape at anterior ventral.

Sculpture: Of comarginal lines and 8-12 low radiating ribs over the dorsal part of the shell, these ribs obscure or lost in large shells. Margin: Inner margin smooth with a few septa at the anterior tip. Ligament: External on a narrow resilifer extending 2/3 length of dorsal margin. Hinge: Lacking teeth. Pallial Musculature: Anterior adductor scar small at the anterior end behind the septa, posterior adductor scar large almost central; nacreous area not divided confined to anterior part of shell. Periostracum: Obscure. Colour: Shades of brownn.

Distribution & Ecology

Mostly in mixed muddy sediments offshore to the shelf edge. Once distributed widely across the western area it is now a very rare and threatened species. See http://jncc.defra.gov.uk/_speciespages/123.pdf for UK action plan.

Depth Range
Continental Shelf (to 200m)

Additional Information & Related Species

Additional Comments

Wrongly synonymised with A. pectinata (an Indo-Pacific species) due to Hanley (1855) writing that the engraving by Gualtier of an European shell was representative of the species, comparing the shell with the few features given in the diagnosis of pectinata, described from Indian shells.

The two species:
Atrina fragilis and A. pectinata are geographically isolated - fragilis is European and pectinata from Indo-Pacific - and each is included in a different subgenus; fragilis in Atrina and pectinata in Servatrina.

Related Species

Pinnoidea : Pinnidae


Listed are literature citing Atrina fragilis (Pennant, 1777). Reference containing the species Type Description is highlighted.

Hanley S 1855. The shells of Linnaeus (Ipsa Linnaei Conchylia) Williams and Norgate, London.
Linnaeus C 1758. Systema Naturae. Editio decima. 1. Regnum Animale Holmiae, Laurentii Salvii. 824pp.
Pennant T 1777. British Zoology vol.IV. Crustacea, Mollusca, Testacea London, B. White. 154pp, 93pls.
Rosewater J 1961. The family Pinnidae in the Indo-Pacific. Indo-Pacific Mollusca. 1 (4): 501-632.


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Record last modified: 22/03/2016