Most species lack rhizines (root-like attachment organs on the lower surface) that are otherwise common in members of the Parmeliaceae, and have swollen lobes that are usually hollow.

[4] In 1951 Hildur Krog considered the morphology and chemistry of this group of species to be distinctive and reinstated the genus Hypogymnia.

[4] In 1974, Krog published an account of three Northern Hemisphere Hypogymnia species that grow on acid rock in arctic and alpine habitats.

[6] This biologically discontinuous assemblage of species was segregated from Hypogymnia by Trevor Goward under the genus name Brodoa in 1986.

The family Hypogymniaceae has been proposed in the past to contain the genus and other similar hypogymnioid lichens,[7] but this taxonomic arrangement has not been widely accepted by other taxonomists.

[8] For example, Krog argued that no critical characters had been suggested that could be used as a defining familial characteristic.

[9] In the Parmeliaceae, Hypogymnia belongs to the hypogymnioid clade along with the genera Arctoparmelia, Brodoa, and Pseudevernia.

Molecular analysis showed that Cavernularia needed to be subsumed into Hypogymnia in order for the latter genus to be monophyletic.

The colour of the ceiling of the tubes (the medullary surface) is dark brown or white, and is often used as a characteristic to distinguish between species.

Although many recent lichen floras and manuals describe Hypogymnia as lacking rhizines, a 2015 study challenges the universality of this assertion.

In all cases where these attachment organs are found, however, they are few in number and are sparsely distributed on the lower thallus surface.

[11] The apothecia of Hypogymnia are lecanorine in form with a constricted base and are often raised or shaped like an urn.

In tropical to subtropical locations, Hypogymnia appears to be restricted to high elevations, where temperatures are cooler.

Examples include monitoring atmospheric nitrogen and sulphur deposition in Norway,[24] the accumulation of mercury downwind of chloralkali plant in Wisconsin,[25] and pollution from several toxic heavy metal elements following the closure of a large mine waste dump close to Zlatna, Romania.

[26] It was also used to help evaluate the levels of radionuclides deposited in the environment after the East Urals (1957) and Chernobyl (1988) nuclear accidents.

[29] In 15th-century Europe, Hypogymnia physodes was one component (in addition to Evernia prunastri and Pseudevernia furfuracea) of the popular drug "Lichen quercinus virdes".