We haven’t had enough fossil penguins here, so let me rectify that deficiency. Below the fold you’ll find a reconstruction of Waimanu, a 61-62 million year old penguin that was discovered in New Zealand.
Oh, and Carl Zimmer has posted a photo of the bird with its skin and feathers on.
This penguin-like bird is strongly adapted for wing-propelled diving, and it appears in the fossil record only 3-4 million years after the K/T boundary. Either it was remarkable precocious, or as the authors favor, the radiation of modern birds occurred well before the extinction of the dinosaurs. They estimate that the neornithine radiation began 90-100 million years ago, in the late Cretaceous. The end of the Cretaceous must have been an interesting time in the skies—the archaic bird groups, the modern neornithines, and the pterosaurs all overlapped in time, and shared many of the same environments.
Slack KE, Jones CM, Ando T, Harrison GL, Fordyce RE, Arnason U, Penny D (2006) Early Penguin Fossils, plus Mitochondrial Genomes, Calibrate Avian Evolution. Mol Biol Evo, preprint in advance of publication.