[6] All Crypturellus are in the family Tinamidae, thus are classed as ratites, making them relatives of the cassowary, emu, kiwi, ostrich and rhea.

[7] The exact distribution limits of certain subspecies, however, are unclear; notably, the population between the Madeira and Purus Rivers (between the generally-reported range of C. u. adspersus and C. u. yapura) and the population between the Tapajós and Araguaia Rivers (between the generally-reported range of C. u. adspersus and C. u. vermiculatus) appear not to have been assigned to subspecies.

[4][11] It has a whitish throat, and the remainders of its underparts are olive-grey to buff with dark vermiculation on its lower flanks and vent.

[4][8][13] The nest of the undulated tinamou consists of a depression on the ground, where the female lays around three glossy vinaceous, pink or light-grey eggs.

The song, commonly given throughout the day, consists of a deep, three- or four-noted whistle, which has been described by the onomatopoetic com-pra pan ("buy bread" in Spanish)[11] or eu sou jaó ("I am undulated tinamou" in Portuguese).