Species Account

Genaxinus eumyarius (M Sars, 1870)

Thyasiroidea : Thyasiridae

Tebble name: n/a
Smith & Heppell name: Thyasira eumyaria (M Sars, 1870)

To size: To 2.5mm. Shell Structure: Fragile. Equivalve: Equivalve. Equilateral: Equilateral. Tumidity: Slightly inflated. Outline: Oval, higher than long, posterior weakly angulate with a short, gently sloping posterior dorsal margin, a steeply sloping posterior margin and weakly angulate, curved ventral margin; anterior dorsal margin straight, steeply sloping into rounded anterior. Contour: Umbos low; auricle indistinct; posterior area flattened but not sulcate.

Sculpture: Of concentric lines with radiating striations within the shell. Margin: Inner margin smooth. Ligament: Ligament sunken, short. Hinge: Hinge weak, teeth absent but anterior hinge plate slightly thickened. Pallial Musculature: Adductor muscle scars raised and extending into umbonal cavity these visible through the shell creating a pair of white rays. Periostracum: Transparent. Colour: White, ferruginous deposits confined to anterior and posterior dorsal areas. Additional Characters: 1 demibranch.

Distribution & Ecology

Unknown from the shelf around Britain and Ireland but is present in shelf waters in Norwegian fjords. Widely distributed on the British and Irish slope mostly around 800-1600m. Suspension feeder, gills with only 1 demibranch; lacks symbionts.
Gill anatomy – Dufour, 2005.
Gross anatomy – Payne & Allen, 1991.

Depth Range
Continental Shelf (to 200m)
Continental Margin Zone (200 - 500m)
Bathyal (500 - 2000m)

Additional Information & Related Species


Listed are literature citing Genaxinus eumyarius (M Sars, 1870). Reference containing the species Type Description is highlighted.

Dufour S C 2005. Gill anatomy and the evolution of symbiosis in the bivalve family Thyasiridae. Biological Bulletin. 208: 200-212.
Olabarria C. 2005. Patterns of bathymetric zonation of bivalves in the Porcupine Sea Bight and adjacent abyssal plain, NE Atlantic. Deep-Sea Research I. 52: 15-31.
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.
Sars M 1870. Bidrag til kundskab om Christianiafjordens Fauna. Nyt Magazin for Naturvidenskaberne. 17: 113-232.


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Record last modified: 17/05/2016