Scientists have numerous hypotheses about the origin of birds， and three hypotheses are very influential． One， which says that birds came from dinosaurs， has arguably become the dominant hypothesis．

Epidexipteryx hui is a Maniraptora， which means literally hand snatcher， and is a type of dinosaurs close to birds． Maniraptora belongs to the theropoda suborder， and is believed to be the ancestor of Archaeopteryx， the earliest bird． Archaeopteryx lived around 150 million years ago， but the fossils of the most ancient species of Maniraptora discovered are dated back 125 million years； so these species lived in a period too late to be the ancestor of Archaeopteryx． Some scientists who believe that birds came from dinosaurs have concluded that some earlier species of maniraptora must exist， and these are the real ancestors of the Archaeopteryx．

Epidexipteryx hui lived about 176 million to 146 million years ago， a period before Archaeopteryx， which provides the missing link in the transition from dinosaur to bird， according to Zhang．

There are two criteria to identify the origin of a species， from age or from bone structure． “Both criteria prove that Epidexipteryx hui is an ancestor of birds，“ said Zhou Zhonghe， one of the co－authors of the paper on Epidexipteryx hui．

The bone structure of Epidexipteryx hui is unique in its four long ribbon－like tail feathers． Although the tip of the plumes could not be found， the end attached to the tailbone was well preserved． The remaining part of the plume is 20 cm long． Previously， fossils of some Archaeopteryxes with ribbon－like tail feathers were discovered in China， which are dated back 137 million to 67 million years， in the Cretaceous period， including the fossils of Confuciusornis and Protopteryx．

The hip of Epidexipteryx hui consists of iliac， pubis and ischium bones． The hip configuration is similar to that of Epidendrosaurus， with the front tip of the iliac raising up sharply， the pubis shorter than the ischium， and the ischium expanding toward the tip． The structure closely resembles that of a bird．

Another unique feature of Epidexipteryx hui is that it has fewer pieces of coccygeal vertebrae than regular dinosaurs． While dinosaurs usually have several scores of coccygeal vertebrae bones， Epidexipteryx hui only has 16．

Although the limbs of Epidexipteryx hui were covered with feathers， it did not have wing feathers， which suggests that it could not fly．

Scientists cannot tell the gender of the Epidexipteryx hui discovered， but suggest that it could be a male， as modern birds with ostentatious tails tend to be males． They flaunt their pretty tails to attract female birds．

Other significant discoveries

In 1996， the fossils of some small feather－covered dinosaurs in the Theropoda suborder were discovered in China． The structure of their feathers is the same as that of modern birds， with a well－developed shaft and barbs． Because of their similarity to birds， scientists named them Sinosauropteryx．

In 2000， Zhang Fucheng and Tian Zhong published a paper in Science， announcing the discovery of Protopteryx fossils， which revealed the origin of feathers．

In 2005？the fossil of a Gigantoraptor was discovered in Erlianhot， Inner Mongolia， a place that is rich in dinosaur fossils． After two years of research， Xu Xing identified this fossil of a large Theropod to be the largest fossil of a bird－like dinosaur． This discovery was listed among the 2007 Top Ten Scientific Discoveries by Time magazine．

Before Xu‘s discovery of the Gigantoraptor， scientists believed that the bigger a dinosaur was， the less likely it was to be related to birds． The Gigantoraptor had a living body mass of 1，400 kg， and stood five meters tall and eight meters long． It is incredible that such a gigantic creature could be a close relative of modern birds． Xu， 39， is the Chinese paleontologist who has discovered the largest number of dinosaur species．

New tool

“We used several methods to identify Gigantoraptor， including cladistic systematics，“ Xu said． Cladistic systematics is a method that quantifies the features of creatures， and uses the data to unlock evolutionary relations between species．

Xu and his fellow researchers used two data matrixes to position Gigantoraptor in the evolutionary tree． The first matrix has data about 251 features of 59 dinosaur species that are close to birds， and the second matrix contains data for the evolutionary process of Oviraptorosauria， the dinosaurs that were suspected of stealing others‘ eggs． The analysis positioned the Gigantoraptor between the most ancient and most recent Oviraptorosauria species．

The traditional research on vertebrate paleontology is primarily qualitative． Researchers usually describe the morphological features of a fossil and analyze its position in the evolutionary process and how it is related to different species． Researchers‘ experience is important， and researchers often have different judging standards， so their conclusions tend to be somewhat subjective． The modern research method based on data is more accurate and can be validated． An anonymous reviewer of Nature recommended the research methods used by Xu to other researchers．

“Technologies such as cross－section CT scans can provide researchers with information that cannot be obtained by conventional means， and which can be used to rebuild a dinosaur‘s brain structure and study motion patterns through animation，“ Xu said．

For a long time， the study of evolution was based on paleontological and morphological information collected from fossils． With the rapid development of molecular biology， now many scholars study evolution by analyzing molecules， cells or embryos． “We hope to use the method of development biology to study the origin of birds， so that we will get a better understanding of the evolutionary process，“ Xu said．