[ad_1]
The discovery of a 127 million year old fossil in northeastern China fills an important evolutionary gap between modern birds and winged creatures resembling the dinosaurs that preceded them.
To say that birds have evolved from dinosaurs is not entirely accurate. Technically speaking, birds are dinosaurs. It turns out that they represent the only line of dinosaurs that escaped extinction 65 million years ago. Today, there is an astonishing 18,000 species of birds on Earth, which proves how much dinosaurs still inhabit the planet.
Despite their omnipresence, the origin and early evolution of birds are still not well understood. Fortunately, a series of new fossil discoveries in recent decades, mostly from China, have brought important new information on this critical stage of dinosaur evolution. The latest developments in this field, details of which were published today in the Proceedings of the National Academy of Sciences, are the discovery of a 127-million-year-old bird fossil found near the village of Shixia in China's Hebei Province.
As lead author Min Wang and his colleagues at the Chinese Academy of Sciences, this genus and this newly identified species, named Jinguofortis perplexus, existed at a crucial stage in the evolution of the flight. It did not have a long bony tail like other flying dinosaurs (the famous Archeopteryx being a good example), but a squat tail typical of modern birds. Unlike flying birds, we see today J. perplexus had not yet developed a range of flying feathers on his truncated tail.
Short-tailed flying birds that end in a compound bone are usually classified as pygostylian birds. Scientists are eager to understand the evolutionary stages leading to the emergence of these short-tailed avians, which is why the discovery of J. perplexus is a big problem. In fact, this new species now represents the second known branch of pygostylian birds.
In addition to its short tail, this early Cretaceous bird had several other important characteristics. He had a wingspan of 69.7 centimeters (27 inches and a half), and his jaw contained a row of small sharp teeth similar to those of his theropod parents (yes, this chicken on your plate shared a common ancestor). with tyrannosaurus and velociraptors). The fossil also contains remnants of gizzard stones, which strongly suggests J. perplexus was a plant eater. Fascinating, and unlike other early risers, her third finger consisted of only two bones – an early example of a species of bird reducing or fusing her bones (more details on this subject). ).
The unique shoulder joint of J. perplexus also tells us something about his flying abilities. The major bones of his shoulder are fused together to form a scapulocoracoid or fused scapular girdle (unlike modern flying birds, which have a narrow joint between the unmerged bones). Researchers say it could have helped birds grow faster and reach maturity faster than normal. More importantly, this configuration suggests the presence of an evolutionary variety, or developmental plasticity, in the development of flight. Given his body and his feathers, J. perplexus probably stolen slightly differently from the birds of today. According to the researchers, its short, broad wings suggest that it lived in dense forests.
"The authors of this publication are among the largest authorities in the field of palaeontology of bird-tailed dinosaurs and have provided another clear description of a new taxon," said Dennis Voeten, paleontologist at Palacký University in the Czech Republic. study, told Gizmodo. "This work seems to offer a very popular piece of the puzzle, namely the first evolution of flying dinosaurs."
Among the discoveries, Voeten found the most surprising shoulder bone fusion.
"For me, this illustrates a new point of view that is starting to grow: the early evolution of flying dinosaurs was not a direct route to modern bird flight, but a great diversity of evolutionary solutions to opportunities. offered by the flights. . "Dinosaurs may have" experimented "with different flight styles and degrees of flight. [flying] the skill that disappeared with non-avian dinosaurs. "
The fused fingers also caught the attention of Voeten.
"The hand of Jinguofortis represents a next step that already resembles the very small hand of modern birds, in which the bones of the fingers have merged into elements able to cope effectively with the constraints associated with feather flying, "he said. "The recognition of this evolution in Jinguofortis allows us to better reconstruct the calendar and the nature of the particular adaptations that reflect evolutionary stages [non-flying] dinosaurs with dinosaurs resembling birds able to fly feathered. "
Voeten says the discovery of more fossils, both inside and outside of China, will further strengthen this line of inquiry, both in terms of understanding of J. perplexus and his place in the large family bird tree. Much remains to be learned about this important step in bird evolution, but every new discovery of fossils is becoming clearer.
[PNAS]Source link
