A new, slightly younger, and more birdlike species of Archaeopteryx has been identified. Where other Archaeopteryxes look like a midpoint between birds and therapod dinosaurs, this one has more in common with the creatures we see today. It cements the case that these are the true ancestors of birds, and allows us to see the order in which some modern features made their appearance.
In the Late Jurassic, some 150 million years ago, southern Germany was a shallow sea, dotted with tropical islands. Like an ancient Galapagos, the diversity of these islands apparently encouraged rapid evolution. Some bird-like features of the small dinosaurs on these islands may have been even more ancient, but the 12 specimens we have found represent the first evidence of an animal that combined them into something resembling modern avians.
Nevertheless, paleontologists have continued to debate whether today's birds descend from this small corner of the world. Dr Benjamin Kear of Uppsala University believes the identification of Archaeopteryx albersdoerferi will settle that.
A. albersdoerferi had air-filled bones, like modern birds, the team report in Historical Biology. The wishbone had more room for flight muscles to attach, the skull was fused, and there were fewer heavy teeth than other Archaeopteryx. All of these are consistent with a lifestyle dependent on flight. Meanwhile, debate remains as to whether other Archaeopteryx could truly fly short distances or whether they merely glided.
A. albersdoerferi lived approximately 400,000 years later than any of the other Archaeopteryx specimens we have found. It was encased in the Mörnsheim Formation, a distinctly younger deposit than the strata in which all other known Archaeopteryx occur.
"Significantly, however, when we examined the evolutionary relationships of various species of Archaeopteryx we found that its flight-related characteristics had appeared separately from those of more advanced bird-line dinosaurs, implying that flying lifestyles have developed more than once,” Kear said in a statement.