The red algae Osmunda pinnatifida has a cartilaginous frond and a flattened body with an erect and branched thallus. O. pinnatifida is perennial and can be found attached to the rocky substratum by its stoloniferous branches and basal crust. Its size can reach 15 cm in length. However, depending on its proximity to the shore both color and size can also vary, gaining a yellow-greenish color and smaller dimensions the closer it gets to the shore.