The callus is about 2.5 mm (0.1 in) long with its central part crowded with many shiny, dark reddish hair-like glands and the tip is about 1 mm (0.04 in) wide with shiny black glands.

[2] Arthrochilus aquilus was first formally described in 2004 by David Jones from a specimen collected in the Heathlands Reserve near the tip of Cape York.

[3] The specific epithet (aquilus) is a Latin word meaning "dark coloured" or "blackish".

[4] The dark elbow orchid grows in forest on the northern part of the Cape York Peninsula.

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