The genus Nocardiopsis was shown to be phylogenetically coherent and to represent a distinct lineage within the radiation of the order Actinomycetales. The closest relatives of the genus Nocardiopsis are members of the genera Actinomadura, Thermomonospora, Streptosporangium, and Microtetraspora. The intrageneric structure of the genus Nocardiopsis is shown to consist of a highly related species group containing Nocardiopsis dassonvillei, Nocardiopsis alborubida, and Nocardiopsis antarctica and a second group of less highly related species comprising Nocardiopsis alba subsp. alba, Nocardiopsis alba subsp. prasina, and Nocardiopsis listeri. Nocardiopsis lucentensis occupies a position intermediate between the two species groups. The results of a 16S ribosomal DNA sequence analysis are generally consistent with the available chemotaxonomic, phenotypic, and DNA-DNA hybridization data. The phylogenetic position and the morpho- and chemotaxonomic properties of Nocardiopsis species support the creation of a family for the genus Nocardiopsis, Nocardiopsaceae fam. nov.
