H. Gadow, Bronn's Thier-Reich, Aves, Syst. Theil. 1893, p. 90.
H. Gadow, Bronn's Thier-Reich, Aves, Syst. Theil. 1893, p. 90.
A pygostyle is occasionally found in Struthio and Apteryx.
P. L. Sclater, P.Z.S. 1895, p. 401.
Argentine Ornithology, ii. 1889, p. 220.