Carl Zimmer in the New York Times:
Penguins are some of the most improbable animals on the planet. They have wings and feathers but cannot fly. They are not fish, but they have been recorded as deep as 1,755 feet underwater. And the most improbable is the emperor penguin, which waddles across 70 miles of Antarctic ice to reach its breeding grounds. New research on penguin DNA suggests that the emperor also has the most ancient lineage of living penguins.
Scientists have long recognized a link from penguins to petrels and albatrosses. While albatrosses have more conventional bird bodies, they share subtle traits with penguins, like the arrangement of beak bones. They are generally considered the closest living relatives of penguins.
Penguins’ ancestors probably began their evolutionary march while Tyrannosaurus rex walked the earth. In a paper to be published in The Proceedings of the Royal Society of London, Canadian scientists investigated the origin of penguins by studying their genes. They analyzed segments from three genes, comparing their sequence in all 18 species of penguins and in other birds.
More here.