We describe a new species of Ecnomiohyla from the vicinity of El Valle de Anton, Cocle, Panama. This is a large species that differs from similar species in the genus by details of the prepollex, webbing, and by the presence of a distinct expanded crista lateralis with medial proximal point. We provide descriptions of the adult and subadult, as well as the tadpole. We provide natural history information including observations of individuals gliding from the forest canopy, reproduction in tree holes, and male territoriality and care of the tadpoles. This species is currently known only from the immediate vicinity of El Valle de Anton, and we have observed numbers of this species in the wild to decrease dramatically following the recent epidemic of amphibian chytridiomycosis in the region.