The Southern pigfish was first formally described in 1846 as Agriopus leucopaecilus by the Scottish naval surgeon, naturalist and Arctic explorer John Richardson with the type locality given as "South Australian seas", although this was probably New Zealand.

[3] The southern pigfish has smooth skin and no spines in the anal fin.

The profile of the head is nearly vertical between the eye and the origin of the dorsal fin.

[1] The Southern pigfish is a sedentary species which swims slowly and rests on the substrate for long periods.

The long snout is used to probe in crevices, seaweed and sand to find the crabs, worms, and other benthic invertebrates that this species feeds on.