The type specimen was collected on sheltered granite ledges in Eucalyptus woodland on the eastern slopes on Tinderry Peak in New South Wales.

[2] Parmelia protosignifera has a thick, leathery thallus, pale grey to brownish in colour, measuring 8–15 cm (3–6 in) in diameter.

Apothecia are common, and they are 4–8 mm (0.16–0.31 in) wide with a concave disc and pseudocyphellae on the margin of the exciple.

[1] Parmelia protosignifera is morphologically quite similar to Notoparmelia signifera, a species with which it has been previously confused, and after which it is named.

The two lichens can be distinguished chemically: P. protosignifera has salazinic acid in the medulla, resulting in a K+ yellow-dark red spot test, while N. signifera contains protocetraric acid, which leads to a K+ pale yellow-brown spot test.