Specimens length varied from 20 to 60 mm, cartilagionous. Main axes distinctly flattened, often narrowed at base, ultimate branches short, often opposite, spine-like or spathulate. Displays the crimson to purplish red.

Relevant characteristics: Lower-intertidal and subtidal low-light habitats, clear pinnate branching, and distinctly flattened main axis.

(Source:http://macoi.ci.uc.pt/spec_list_detail.phpspec_id=81&searchSpecies=Gelidium+spinosum+%28S.G.+Gmel.%29+P.C.Silva)