Parts of the skeleton of P. haydenianus are known and this species was about 75 cm long, comparable to the related Didymictis and the modern day Asian civets.

The characteristic carnassials of carnivores were already clearly developed in Protictis, but the long and pointy teeth show that insects were still a major component of this diet.

[8] Fossils of Protictis are found in the United States and Canada and date mainly from the early to late Paleocene.

The holotype of first discovered species (a part of the upper and lowe jaw) were described in 1882 by Edward Drinker Cope based on finds in the San Juan Basin in New Mexico and classified as Didymictis haydenianus.

William Diller Matthew described Protictis as a subgenus of Didymictis in 1937 and in 1966 MacIntyre classified it as a separate genus.