The upper region of the red pigment in Rhizophysa filiformis is positioned around the apical pore. There are no partitions; instead, the space is filled with hypocystic villi containing large gas-gland cells. The siphosome is slender and elongated, featuring numerous pale green gastrozooids found exclusively on one side of the stem. The androphore and gynophore share similar shapes, sizes, and positions on the branchlets. The androphore possesses a spadix carrying sperms. The gynophore is oval-shaped, and ova are situated on the sinuous band, resembling the arrangement in P. physalis.