Fossil found in China scrambles avian evolution

Prefer us on Google Learn More Facebook Twitter Bluesky WhatsApp SMS Email Print Copy article link Save WILL DUNHAM Reuters Scientists discovered the fossil of a crow-sized bird that lived in China roughly 150 million years ago and possessed undersized wings that may have made it more of a runner than a flier — a discovery that paints a more complicated picture of early avian evolution. The new Jurassic Period species, Yuezhuornis yangyuanensis, represents one of the earliest-known birds, similar in age to the famous Archaeopteryx from Europe. Yuezhuornis is puzzling for an early bird in that it seems already to have diminished the ability to fly in favor of running on the ground, perhaps somewhat like a roadrunner — a fast runner but clumsy flier that rarely takes to the air. "Yuezhuornis challenges the traditional paradigm that the avian body plan evolved almost exclusively under the selective pressures of flight," said paleontologist Min Wang of the Institute of Vertebrate Paleontology and Paleoanthropology, part of the Chinese Academy of Sciences, who helped lead the study published on Wednesday in the journal Nature. 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Asked if Yuezhuornis may have lived like a roadrunner by mostly running but flying in short bursts when necessary, Wang said, "Yes, that is likely." The nearly complete fossil was unearthed in Fujian Province in southeastern China. Birds evolved during the Jurassic from small feathered dinosaurs, but fossils showing precisely when this occurred and how it unfolded are lacking. Archaeopteryx long was the oldest-known bird, but a small number of others of similar age, like Yuezhuornis, have now been found. Yuezhuornis, which weighed an estimated 1.8 pounds, presented a mosaic of anatomical traits, combining avian and dinosaurian characteristics. Its forelimbs were fully developed wings, though they were too small compared to the rest of the body to have allowed for robust flying. It also had the slender cranial bones of a bird and a birdlike pelvis. On the other hand, Yuezhuornis had a sickle-shaped claw on its flexible second toe similar to that of meat-eating dinosaurs like Deinonychus, Velociraptor and Troodon — a dangerous weapon useful for a terrestrial hunter. In fact, Wang said, Yuezhuornis may have competed for prey with small non-bird dinosaurs. It had relatively large, closely packed and serrated teeth lining its jaws, typically present in certain carnivorous dinosaurs but not birds. In addition, it had a long and bony dinosaurian tail, as all the earliest-known birds did. Archaeopteryx combined avian and dinosaurian traits, too, but its well-proportioned wings showed it was built for flying. The wings of Yuezhuornis, by contrast, were a third shorter than its legs.Comparisons with 377 extant bird species showed that the limb proportions of Yuezhuornis most resembled those of ground-dwelling avian species like pheasants. Yuezhuornis is believed to have shared with Archaeopteryx a common ancestor that lived earlier in the Jurassic, Wang said. It also is possible that Yuezhuornis represents an evolutionary experiment that emerged separately from the main avian evolutionary lineage, Wang said. Wang said he did not expect to see a species so close to the evolutionary origins of birds that appears to have possessed limited or perhaps no ability to fly. "It surprises us," Wang said. University of Edinburgh paleontologist Steve Brusatte, an expert in dinosaurs and birds who was not involved in the study, said, "Yuezhuornis is one of those discoveries that throws up more questions than it gives answers." Brusatte, who authored the recent book "The Story of Birds" exploring avian evolution, said Yuezhuornis appears to be an actual member of the bird evolutionary lineage. 0 Comments Love 0 Funny 0 Wow 0 Sad 0 Angry 0 Be the first to know Get local news delivered to your inbox! 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