[1] Found in Brazil, it was described by lichenologists André Aptroot, Aline Anjos Menezes, and Marcela Cáceres in 2013.

The thallus of P. multiseptatum is ecorticate and whitish-grey in color, with the distinctive feature of fluorescing yellow under ultraviolet light.

This lichen closely resembles Polymeridium quinqueseptatum, with the primary distinguishing characteristic being the UV+ (yellow) thallus.

The ostiole is apical, and the hamathecium is interspersed with oil droplets, with filaments profusely anastomosing.

The type specimens were collected in Chapada do Araripe, Ceará, at an altitude of 800 m (2,600 ft), where it was found growing on tree bark.