David J.Galloway described Placopsis imshaugii as a new species in honour of the American lichenologist Henry Andrew Imshaug, who made contributions to the study of lichens in South America.

The type specimen was collected in October 1969 at Desolación Island, a treeless anchoridge in the Fondeadero Nassau region of Chile.

The grey-brown to pinkish-brown marginal zone contrasts with the orange-brown or rust-brown upper surface found centrally.

Each of these species exhibits unique characteristics, such as the presence of white effigurate (with a defined form) maculae in P. baculigera, the orange-yellow to red-brown convex lobes in P. bicolor, the white laminal pseudocyphellae in P. elixii, and the grey-blue scattered laminal soralia in P. lateritioides.

It colonises hard siliceous rocks on scattered outcrops on ridges and open hillsides, occasionally associating with Aspicilia sp., Placopsis gelida, and rust-coloured species of Porpidia.