Happy feet: why a 61m-year-old penguin foot has researchers dancing for joy

Early evolution of modern birds is fuzzy, so a fossil foot showing unexpected diversity in penguins shortly after the dinosaurs went extinct is big news

The theory that birds descended from bipedal dinosaurs, Coelurosaurs to be exact, is now well-established within the palaeontological community. With that one out of the way, bird palaeontologists can focus on more pressing issues, such as the origin and evolution of Neornithes, the group of birds that comprises all living birds. Several groups of extinct birds are known to have existed alongside the dinosaurs, such as the aquatic diving birds Hesperornithiformes, the large, toothed Ichthyornithiformes, and the "opposite birds" Enanthiornithidae, named after the distinct anatomy of their shoulder girdle. None of them gave rise to the birds we see in our backyard today.

The early evolution of modern birds is fuzzy, to say the least. Models based on molecular clocks place the origin of Neornithes as far back as the Early Cretaceous, whereas others suggest that modern birds did not diversify until the Late Cretaceous (see Brocklehurst et al., 2012 for a discussion). The sparse fossil record of Mesozoic Neornithes does little to clear things up.