[3][4][5] The holotype adult of P. incerta, specimen number SMNK PAL 5352 is housed in the collections of the State Museum of Natural History Stuttgart, while the partial paratype adult, specimen number SMNS 66000/255, is part of the State Museum of Natural History Karlsruhe, Germany.

[3] The specimens are preserved as compression fossils in finely laminated siltstones, which were recovered from outcrops of the Nova Olinda Member of the Late Aptian Crato Formation in Northeastern Brazil.

The species is older than P. incerta, having been recovered from Rudgwick Brickworks which mined sediments of the Barremian Upper Weald Clay Formation.

[5] The Brazilian fossils were first studied by the paleoentomologists Vladimir N. Makarkin of the Far Eastern Branch of the Russian Academy of Sciences and Federica Menon from the University of Manchester in England.

[3] The specific epithet "incerta" is derived from the Latin incertus, in reference to the uncertain relationship of the genus within Ithonidae.

[4] Overall the vein structure of Principiala is most similar to the genus Allorapisma, known from Ypresian fossils found in the northwestern United States.