A variety of subspecific arrangements had been regarded as colour variation across an east to west cline, although the geographically distinct morphology came to be acknowledged in the late twentieth century. Further support was given in a genetic study published in 2005 showed that the two subspecies of the long-tailed finch were separated from each other by the Kimberley Plateau–Arnhem Land Barrier around 340,000 years ago, and their ancestors diverged from the black-throated finch ("P. cincta") across the Carpentarian Barrier 600 thousand years ago.