Membranoptera alata is a small red marine alga growing to a length of no more than 20 cm.

Its fronds are up to 2.4 mm wide and monostromatic, that is formed of a thin layer of cells,[1][2] narrow and branching in one plane.

Spermatangial sori, the male gametes, develop in patches near the tips of the branches.

[3] Growing on rock or large algae epiphytically and epilithically in the low littoral and upper sub-littoral.

Elsewhere in the North Atlantic on the European coasts it has been recorded from Greenland, Iceland to Spain.