A new viviparous halfbeak, Nomorhamphus aenigma, new species, from the upper stream of the Cerekang River in central Sulawesi, Indonesia is described. The new species is distinguished from all other zenarchopterids by the complete absence of elongate lower jaws. Although secondary loss of elongate jaws is also known from several hemiramphids, N. aenigma, new species, is clearly different from them by having no elongate jaws throughout ontogeny.
