Milne-Edwards, Oiseaux Fossiles de la France, ii. 1868, p. 58.
Dames, Svensk. Ak. Handl. Bihang, xvi. 1890, Part IV. No. 1, pp. 4-11.
Gibson, Ibis, 1880, pp. 165-167; Hudson, Argentine Ornithology, ii. 1889, pp. 119-122.
Chauna has a dilatation near the middle of the trachea.
Cat. Birds Brit. Mus. xxvii. 1895, pp. 23, 24.