Species Account

Thyasira biplicata (Philippi, 1836)

Thyasiroidea : Thyasiridae

Tebble name: n/a
Smith & Heppell name: n/a

Notes on Nomenclature

Previously here as Thyasira polygona, but since synonymised with T. biplicata

To size: To 8mm. Shell Structure: Thin. Equivalve: Equivalve. Equilateral: Equilateral. Tumidity: Tumid. Outline: Ovate-polygonal; anterior dorsal margin long, steeply sloping to narrowly rounded anterior margin; ventral margin a broad curve; posterior deeply sinuose with prominent posterior and marginal sinuses. Contour: Posterior sinus and sub-marginal sinus very pronounced, auricle very high and distinctly projecting above the dorsal margin. Lunule distinct.

Sculpture: Smooth except for incremental lines and growth stops. Margin: Inner margin smooth. Ligament: External but deeply sunken within auricle. Hinge: Hinge plate narrow, a weak flange like protuberance in RV. Pallial Musculature: Muscle scars obscure. Periostracum: Thin not persisting. Colour: Shell white. Additional Characters: 2 demibranchs.

Distribution & Ecology

Known from few records at shelf depths in the central North Sea and from deeper sea lochs on the west coast of Scotland. Chemosymbiotic, sporadic occurrence but mostly in deeper shelf situations. The gills have 2 demibranchs is and similar to T. flexuosa. Ecological separation from T. flexuosa not understood.

Depth Range
Continental Shelf (to 200m)

Additional Information & Related Species


Listed are literature citing Thyasira biplicata (Philippi, 1836). Reference containing the species Type Description is highlighted.

Killeen I J & Oliver P G 2002. Thyasira polygona (Jeffreys) (Bivalvia: Lucinoidea), an abandoned taxon with a possible amphi Atlantic distribution. Journal of Conchology. 37: 383-390.
Oliver P G & Killeen I J 2002. The Thyasiridae (Mollusca: bivalvia) of the British continental shelf and North Sea Oilfields. Studies in Marine Biodiversity and Systematics from the National Museum of Wales. BIOMOR Reports. 3: 1-73.
Payne C.M. & Allen J.A. 1991. The morphology of deep-sea Thyasiridae (Mollusca: Bivalvia) from the Atlantic Ocean. Philosophical Transactions of the Royal Society of London Series B. 334: 481-566.
Philippi R A 1836. Enumeratio molluscorum Siciliae cum viventium tum in tellure tertiaria fossilium, quae in itinere suo observavit. Vol. 1 Schropp, Berlin. 267pp, 12pls.
Taylor J D, Williams S T & Glover E A 2007. Evolutionary relationships of the bivalve family Thyasiridae (Mollusca: Bivalvia), monophyly and superfamily status. Journal of the Marine Biological Association of the United Kingdom. 87: 565-574.


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Record last modified: 17/05/2016