The genus contains a single described species, Usomyrma mirabilis, that is known from two Middle Eocene fossils which were found in Scandinavian amber in Denmark.

Usomyrma mirabilis is known from two isolated fossils, the holotype and paratype, both of which were housed in the collections of the Zoological Museum of the University of Copenhagen.

Their 2014 type description of the new genus and species was published in the journal Acta Palaeontologica Polonica.

The specific epithet is from the Latin word mirabilis which translates as "wonderful, marvellous, or miraculous", a nod to the unique morphology of the species.

Dlussky et al thought U. mirabilis represented an ancestral wing venation for the tribe, with a progression in vein reduction being present in Leptomyrmula.

The Leptomyrmex was treated as a descendant genus of the ancestral form Usomyrma in the classification suggested by Dlussky et al.[1] A 2016 study showed the central cell reduction, on which placement of the genus was based, was shown to be derived several times in the subfamily and not specific to the tribe Leptomyrmecini.