The genus was described based on an incomplete, toothless left dentary (now lost) from the Late Cretaceous of Patagonia (in Argentina), probably dating to the Campanian or Maastrichtian.

Initially classified as a putative ceratopsian found in the Lago Colhué Huapi Formation, the lost fragmentary holotype precludes confident referral of this taxon within ornithischians, with some researchers suggesting that it belongs to a hadrosaur instead.

[1] The generic name is derived from Greek notos, "the south", keras, "horn" and ops, "face".

In many later publications the specific name is misspelled "bonarelli", with a single "i", from the incorrect assumption it would be derived from a Latinised "Bonarell~ius".

The fossil, found near the Lago Colhué Huapi in Chubut, was eventually described by Friedrich von Huene in 1929,[2] but it has since been lost.