Species are a fundamental unit for all fields of biology but conceptual and practical limitations have hampered the process of identifying and describing species in many organismal groups. One outcome of these challenges is the accumulation of genetically divergent lineages and morphologically distinctive populations that are ‘known’, but remain of uncertain taxonomic status and evolutionary significance. These lineages are also currently not effectively incorporated into evolutionary studies or conservation planning and management. Here we suggest three ways to address this issue. First, there is a need to develop improved frameworks to systematically capture taxonomically unrecognised lineage diversity. Second, increased utilisation of metadata frameworks will allow better recording and dissemination of biodiversity information. Finally, emerging genomic and analytical techniques will provide powerful new tools to improve our identification and understanding of evolutionary lineages.