Species Account

Lyonsiella subquadrata (Jeffreys, 1882)

Verticordioidea : Verticordiidae

Tebble name: n/a
Smith & Heppell name: Lyonsiella subquadrata (Jeffreys, 1881)

To size: To 3mm. Shell Structure: Thin, fragile. Equivalve: Equivalve. Equilateral: Inequilateral, beaks in the anterior quarter. Tumidity: Moderate. Outline: Rhomboidal, subrectangular with posterior dorsal margin subparallel with ventral margin; posterior dorsal margin long, sloping gently; posterior broadly rounded to subtruncate; ventral margin long gently curved; anterior much narrower than posterior narrowly rounded, deep indentation in front of umbos. Contour: Umbos prominent; shallow radial sulcus down median anterior slope.

Sculpture: Radial lines absent, concentric lines weak; overall with conspicuous spinules these becoming lost in some shells. Margin: Inner margin smooth. Ligament: Opisthodetic, small, internal with a lithodesma. Hinge: Teeth absent but irregular thickenings present. Pallial Musculature: Obscure. Periostracum: Obscure. Colour: Dirty white.

Distribution & Ecology

Allen & Turner (1974) give a large bathymetric range from 298-3340 m from sites across the North Atlantic. The Porcupine material and our shells are bathyal in depth (1000 - 1400m) and are from the Hebrides slope. It is likely to be distributed along the Atlantic Margin.

Depth Range
Continental Margin Zone (200 - 500m)
Bathyal (500 - 2000m)
Abyssal Rise (2000 - 4000m)

Additional Information & Related Species

Key Features & Similar Species

As with many verticordiids the shell is rather variable but differs from L. abyssicola in lacking radial lines and being more rectangular in outline with the posterior margin less expanded and less truncate. In the original Porcupine shells one has virtually no spinules and one has weak spinules; we have a shell from the Hebrides Terrace with strong spinules and we are unsure of the significance of this variation.

Related Species


Listed are literature citing Lyonsiella subquadrata (Jeffreys, 1882). Reference containing the species Type Description is highlighted.

Jeffreys J.G. 1882. On the Mollusca procured during the ‘Lightning’ and ‘Porcupine’ Expeditions, 1868-70. (Part IV). Proceedings of the Zoological Society of London. 1881: 921-952.
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.


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Record last modified: 17/05/2016