Isodrepanium is a genus of a single Neotropical species. The genus has strongly complanate-foliate stems, with leaves that are strongly asymmetric to cultriform. Its leaf cells are uniformly long-flexuose and porose throughout, and its alar cells are weakly developed. The single species of Iso-drepanium was originally described in Homalia, and the two genera are gametophytically similar in having weakly costate, complanate leaves inserted in eight ranks (Florschütz-de Waard 1986; He 1997) with poorly developed alar cells and smooth, cucullate calyptrae. Furthermore, the genera have similar sporophytes: setae elongate; capsules suberect to inclined, short-cylindric; stomata present; opercula obliquely long-rostrate; annuli well developed; exostome densely cross-striate on dorsal (outer) surface; endostome with a high basal membrane and well-developed segments. Plants of Homalia are much more glossy than those of Isodrepanium, and they grow in strongly flattened mats. In addition, the oblong-ovate to oblong-spathulate leaves of Homalia are usually rounded-obtuse and have isodiametric to rounded or rhomboidal upper leaf cells.

The leaves of Neckera and Isodrepanium are somewhat similar in shape. However, many species of Neckera have undulate leaves, and they are never as strongly cultriform as those of Isodrepanium. The genus further differs from Isodrepanium in having short setae (capsules immersed to short-exserted) and a reduced, neckeroid peristome. Isodrepanium has sometimes been placed in the Hook-eriaceae, probably because of a gametophytic similarity to the genus Lepidopilum. Lepidopilum dif-fers from Isodrepanium in having thin-walled, non-porose leaf cells, often plicate and hairy mitrate calyptrae, and a hookeroid peristome.

The name Isodrepanium is combines the Greek isos (equal or like) with drepano (sickle-shaped), and refers to its distinctively shaped leaves.