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J.A. Clarke , D.T. Ksepka , R. Salas-Gismondi , A.J. Altamirano , M.D. Shawkey , L. D’Alba , J. Vinther , T.J. DeVries & P. Baby 2010. Fossil evidence for evolution of the shape and color of penguin feathers. Science, 330, 954–957.
T.L. Hieronymus 2015. Qualitative skeletal correlates of wing shape in extant birds (Aves: Neoaves). BMC Evolutionary Biology, 15, 303.
P. Jadwiszczak & S.D. Chapman 2011. The earliest fossil record of a medium-sized penguin. Polish Polar Research, 32, 269–277.
G. Mayr 2004. Tertiary plotopterids (Aves, Plotopteridae) and a novel hypothesis on the phylogenetic relationships of penguins (Spheniscidae). Journal of Zoological Systematics and Evolutionary Research, 43, 61–71.