[4] P. hilarii is found in southern Brazil (Santa Catarina and Rio Grande do Sul), southward and westward into Uruguay and Argentina, and possibly also in Paraguay and Bolivia.

[5] P. hilarii inhabits streams, lakes, and swamps with abundant aquatic vegetation and soft bottoms.[6]P.

The head is large and flat, gray to olive above, with a pointed snout and two bicolored chin barbels.

[7][6] An omnivorous species, P. hilarii mainly feeds on arthropods, with a preference for copepods, ostracods, and hemipterans.

[9] Females lay eggs twice a year, one clutch between February and May and the other between September and December.