Ptilodus was a relatively large multituberculate of 30 to 50 centimetres (12 to 20 in) in length, which is about the same size as a squirrel. Its feet, legs and long tail suggest it was a good climber, so it very possibly led a squirrel-like lifestyle.[1] The genus was named by paleontologist Edward Drinker Cope in 1881. Cope also mistakenly assigned some material belonging to this genus to Chirox in 1884. Elements from Ectypodus (Jepsen, 1940) and Neoplagiaulax have also been reassigned to this genus.