Caudipteridae, the primitive group of raptor, is one of the earliest dinosaur groups. Its feathers are similar to modern birds, which is of great significance to the early evolution of Raptor and the origin of birds. At present, it is known that 2 genera and 3 species of Apiaceae have been found in the early Cretaceous Jehol biota of western Liaoning Province. Among them, the hands of Zou's tail feather dragon and Dong's tail feather dragon are well preserved. The most prominent feature is that the ring finger of the hand is extremely degraded, with only two short knuckles left. The finger pattern is 2-3-2 type, which is different from the 2-3-4 type of most other non avian theropod dinosaurs. In addition, Yixian tail feather dragon does not preserve hand bones. According to this special finger pattern, shortened tail, loss of acetabular crown on iliac bone and other characteristics, some scholars even believe that tailfeather dragon is not a dinosaur, but a bird that has lost its flight ability.
On April 25, scientific reports published online the latest achievements of Wang Xiaolin's research team of Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences. Qiu Rui, D
It belongs to xingtianlong, a new genus and new species of feather family found in the early Cretaceous Yixian Formation of Wangjiagou, Yixian County, Liaoning Province. The main differences among species of coccygidae include that the lateral fossa of the dorsal spine is close to the dorsal edge of the spine, the length of the scapula is shorter than the humerus, the length of the ulna is close to the humerus, the angle of the radiocarpal bone is small, and the length of the first metacarpal bone is less than 40% of the second metacarpal bone. The results show that Ganqi xingtianlong is a primitive tail feather dragon.
Although the preservation of the ring finger of Ganqi xingtianlong's hand is incomplete, the clear preservation of its ring finger claws and some knuckles shows that its ring finger is not as specialized and reduced as tail feather dragon. In addition, the phalangeal ligament fossa of Ganqi Tianlong is small, while that of tail feather dragon is particularly large. On the whole, the hand characteristics of Ganqi Tianlong are closer to other theropod dinosaurs than tail feather dinosaurs. The researchers took this opportunity to comprehensively sort out the evolution process of egg stealing dragon hand. The results show that the hand evolution of egg stealing dragons is very complex, and there are different evolutionary trends in tailurodaceae, neognathodaceae and egg stealing dragons.
The discovery of Ganqi xingtianlong also provides new information for the evolution of radiocarpal angle of virtual bone dragons. The radiocarpal angle is the included angle between the radiocarpal bone and the radial articular surface and the semilunar carpal articular surface, which is related to the motion angle of the hand and ulna. Previous studies have concluded that during the evolution of theropod dinosaurs to birds, the radial carpal angle generally showed an upward trend. The radial wrist angle of egg stealing dinosaur increased abnormally, reaching 76 ° (the measured data are from tail feather dinosaur), which is not only much larger than other theropod dinosaurs (generally below 40 °), but even more than that of primitive birds. To solve this problem, the researchers measured other well preserved egg stealing dragons with radius and wrist bones and found that their radius and wrist angles were large. However, the researchers note that these measurements either come from extreme late Cretaceous organic groups (tail feather dragon) or advanced egg stealing dragon, which can not well represent the early evolution trend of this group. As a primitive egg stealing dragon with non specialized hands, the radial carpal angle of Ganqi xingtianlong should be closer to the early evolutionary state of the population. The radial carpal angle of Ganqi xingtianlong is 39 °. It is consistent with the overall evolution trend of radial carpal angle of Xugu dragon. It is proved that the radiocarpal angle of egg stealing dragon is actually relatively small in the early stage, but gradually increases in the later evolution and converges with birds.
Gan Qi Xing Tianlong's name "Xing Tian" comes from the Chinese mythological figure Xingtian《 The book of mountains and seas records that Xing Tian was a general who was beheaded in the war. However, after being beheaded, Xing Tian continued to fight with weapons (an axe). Due to the missing head of the new specimen, the researchers took "Xingtian" as their generic name and "Ganqi" as their real name.