Serpocaulon triseriale (Sw.) A.R. Sm. is considered the most widespread species in the genus. It has been recorded from south of Mexico to Bolivia, Paraguay and Brazil. Here, we expand its distribution by reporting a new record from Salta province, Argentina, based on material that was previously misidentified as S. polystichum (Link) A.R. Sm. We compare the S. triseriale and S. polystichum with their relatives (S. attenuatum (Humb. & Bonpl. ex Willd.) A.R. Sm., and S. rex Schwartsb. & A.R. Sm.), providing photographs of the plants in the field, SEM images of the spores and light photos of the rhizome scales to discriminate S. rex from S. triseriale. In addition, distributional records are included.