Known from parts of a right wing – the humerus, ulna and radius bones – the only specimens found so far are housed in the Museum of the Rockies (collection number MOR 1113).

The fossils were found in 1991 by Gloria Jean Siebrecht in the Blackfeet Indian Reservation, namely at Bob's Vacation Site locality TM-088, Glacier County.

Comparing the fossils' size to the wing bones of other ground birds, P. barbarulna would have been relatively small, with a wingspan reaching 1 m (3.3 ft).

This was formed from sediments deposited during what seems to have been a rather cool phase of the Late Cretaceous:[5] sea levels of the Western Interior Seaway at least were apparently very low for Mesozoic standards, though this may also have been due to strong tectonic uplift in the Cordilleran Overthrust Belt.

That there was a temporary though not permanent body of water is indicated by the presence of articulated frog skeletons and the absence of fish and other aquatic animals.