From comparison with its relatives, it can be supposed that it was a small notoungulate with a short tail and long hind legs.

It shared similarities with the slightly older Prohegetotherium, but differed from it in several ways, including its smaller size.

The incisors and canines were directed forward, giving rise to a "false diastema" between them and the backward-directed first premolars.

Ethegotherium was a member of the Hegetotheriidae, a group of small-sized Notoungulates, similar in appearance to lagomorphs.

Later, a study by George Gaylord Simpson, Bryan Patterson and Minoprio himself identified several sufficiently distinctive characteristics for the establishment of a new genus, Ethegotherium (whose name is the anagram of Hegetotherium).