Males have a short, dense tuft of hairs on the front of their jaws.
In the described male and female, the head and thorax are dark reddish brown. The abdomen is mottled greyish brown and beige, with three pairs of humps on its back.
Austrarchaea milledgei is a tiny spider with an elevated front body and two pairs of small horns on the head. Its male holotype was 3.08 millimetres long, with a carapace 1.09 millimetres long and 2.31 millimetres high.
The 2011 study also reported an unresolved question. Specimens collected along Barrington Tops Forest Road in April 2010 showed approximately six percent divergence in the mitochondrial COI and COII sequence data. The authors noted unusually substantial variation in both morphology and genetic information among material from the region.
They proposed that two externally similar species might occur together there. For the revision, northern Barrington Tops material was provisionally treated as this species, with further comparison of males across the region recommended. The identities of a female from Gloucester Tops and a juvenile from Chichester State Forest also remained to be confirmed. The name thus brought together material while leaving explicit questions for future research.
An extinction-risk assessment has not been added yet.
The authors reported in 2011 that this restricted-range species was abundant in Barrington Tops National Park and did not then regard it as of conservation concern. They nevertheless left surrounding specimens in need of identification work. Maintaining forest and clarifying identities and occurrence across localities would improve information for conservation decisions.