[1] According to the World Register of Marine Species Himanthalia elongata is the only member of its genus, Himanthalia Lyngbye, 1819 [2] and the only member of its family, Himanthaliaceae (Kjellman) De Toni, 1891.

[3] Himanthalia elongata is a common brown alga of the lower shore.

The thallus is at first a small flattened or saucer-shaped disc up to three centimetres wide with a short stalk.

In the autumn or winter, long thongs grows from the centre of this, branching dichotomously a number of times.

They bear the conceptacles, the reproductive organs, and begin to decay when the gametes have been released into the water.