The lectotype specimen is housed at the University of Helsinki Herbarium (H), and was designated as such by Robert E. Magill in his 1981 treatment of South African mosses, though it had previously been annotated as a holotype.

[7] The leaves lack a border (technically termed 'elimbate') and are shaped like an elongated oval or reverse teardrop, with a broadly pointed to rounded tip that sometimes has a tiny projection.

The leaves are divided into different sections, with the clasping portion (vaginant laminae) extending about halfway up the leaf length.

[7] The reproductive structures of F. usambaricus can be male (perigonia), female (perichaetia), or both (synoecia), and are found at the tips of the stems.

[6] Fissidens usambaricus is endemic to Africa, where it shows a distinct preference for soil-based habitats, though it can occasionally be found growing on wooden debris, rock surfaces,[6] or termite mounds.

The species is typically found on shady banks and road cuts, though it can also occur near waterfalls and on rocks in or along streams.