In an accompanying article, Lawrence Witmer at Ohio University wrote: "There has been growing unease about the avian status of Archaeopteryx as, one by one, its 'avian' attributes (feathers, wishbone, three-fingered hand) started showing up in non-avian dinosaurs. Perhaps the time has come to finally accept that archaeopteryx was just another small, feathered, bird-like theropod fluttering around in the Jurassic."
If Archaeopteryx was a dinosaur, this means flight evolved at least four times in vertebrates: in reptiles, birds, dinosaurs, and most recently in bats.
Witmer adds that with Archaeopteryx dethroned, more recently discovered fossils, including Epidexipteryx, Jeholornis and Sapeornis, become candidates for the world's oldest bird. On a cautionary note, he adds that the next feathered fossil unearthed in China could easily restore the premier status of Archaeopteryx.
Paul Barrett, a dinosaur researcher at the Natural History Museum in London, said: "The overall picture of birds being descended from meat-eating dinosaurs is now very firmly established. This is an argument over a relatively small rearrangement of some of the twigs on the evolutionary tree close to the origin of birds. It doesn't affect much of our big picture view of how birds came from dinosaurs, but some of the minutiae: the small changes that are important to the biology of the animals.
"This part of the evolutionary tree is very sensitive to small changes in how we interpret the anatomy and the combination of anatomical features we see in these animals as they are discovered. As a result, the structure of that evolutionary tree is very unstable and can flip around. Maybe Archaeopteryx wasn't on the direct ancestral line to birds, but was part of an early experimentation in how to build a bird-like body."
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