As part of a revision of Selaginella subg. Heterostachys in Central and South America, S. hyalogramma Valdespino is described as a new species and illustrated with a line drawing, as well as with scanning electron microscope (SEM) images of leaves, sporophylls, and megaspores. This new species is characterized by non-articulate stems, heteromorphic vegetative leaves with idioblasts on their upper and lower surfaces that are also present on sporophylls, as well as dorsiventral, resupinate strobili and a laminar flap on lower surfaces of dorsal sporophylls. These characters serve to compare it to morphologically similar taxa. In addition, the presence of stomata along basiscopic leaf margins and basiscopic submarginal short or tooth-like hairs on upper surfaces of lateral leaves of this species are reported and discussed. Finally, S. hyalogramma is only known from a single collection made in the State of Táchira, Venezuela, where it grows as an epipetric plant on mossy sandstone areas that may be severely deforested and, hence, it is tentatively considered Critically Endangered (CR) according to IUCN categories and criteria.