The petals and lateral sepals turn backwards against the ovary and are inconspicuous.

[2][3] Arthrochilus byrnesii was first formally described in 1972 by Donald Blaxell from a specimen collected near the South Alligator River.

The description was published in Contributions from the New South Wales National Herbarium from a specimen collected by Norman Byrnes.

[4] In 2002 David Jones and Mark Clements changed the name of this orchid to Phoringopsis byrnesii, but the name has not been adopted by some authorities.

[2][6][7] As with other Arthrochilus orchids, A. byrnesii is pollinated by male thynnid wasps of the genus Arthrothynnus although the species involved is not known.