Polyblastidium squamulosum is a species of corticolous (bark-dwelling), foliose lichen in the family Physciaceae.

[2] It is found in North America.

The species was first scientifically described by the Swedish lichenologist Gunnar Degelius in 1941, who initially classified it in the genus Anaptychia.

[3] William Culberson reclassified it in the genus Heterodermia in 1967.

[4] It was transferred to the newly circumscribed genus Polyblastidium in 2015 by Klaus Kalb.