Asia-Tropical: Assam (Assam present); Philippines (Philippines present), Burma present, Luzon present, N Thailand present, S China present
Assam, Burma, N Thailand, S China. Malesia: Philippines (Luzon).
Copeland (1960) suggested that this may be a form of A. lehmannii. Indeed, in lamina shape and soral disposition it is similar to the specimens from Taiwan usually identified as A. lehmannii. However, both A. proteus and the Taiwan specimens differ from typical A. lehmannii in having sori predominantly in a single row between the veins, whereas A. lehmannii has sori nearly always in double rows. Arthromeris proteus differs from the Taiwan specimens in the rhizome, which has shorter internodes, and the rhizome scales, which have strikingly wide cells. The scales are mostly 8 or 9 cells wide directly above the point of attachment, whereas the corresponding number of cells in A. lehmannii (and in the specimens from Taiwan) is at least twice as many. In both soral disposition and rhizome and rhizome scale structure A. proteus appears to agree better with A. tatsienense (H. Christ) Ching. In the absence of a complete revision of Arthromeris, the exact identity of the few specimens from the Philippines cannot be ascertained.