A new Neotropical species of hornwort, Nothoceros superbus, is described from Costa Rica. The species is distinguished by its large size, strongly costate thallus with crispate-imperforate wings, dioicous condition and green, unicellular spores that are minutely papillose with tubercules dispersed on the borders and the distal face, and sometimes clustered in the center of the distal face. Nothoceros superbus has a combination of Megaceros-like spores and a Dendroceros-like thallus growth-form. The combination of these features supports its placement in the genus Nothoceros in the Dendrocerotaceae. Nomenclatural clarifications on Nothoceros endiviaefolius (Mont.) J. Haseg. and Nothoceros giganteus (Lehm. & Lindenb.) J. Haseg. are made. Based on new molecular and morphological data a new combination, Nothoceros canaliculatus (Pagán) comb. nov., is proposed.