China News Service, Beijing, January 3 (Reporter Sun Zifa) It is a consensus in the academic circle that birds evolved from dinosaurs. The evolution process, especially how the skull and body of early birds evolved independently, has long attracted attention.

　　The latest research by Chinese scientists in the Jehol Biota (135 million to 120 million years ago) has discovered a new genus and species fossil of a skeleton bird, the Heroopteridae - a Cretaceous bird with a dinosaur skull and a weird body, and will It was named "Zhu's craton bird of prey", and through in-depth research on it, it revealed the adaptive evolution process of the skull, scapula and first metatarsal of early birds.

Evolutionary trajectory of the scapula during dinosaur-bird evolution.

Photo courtesy of Wang Min

　　This important research progress on the evolution from dinosaurs to birds was jointly completed by researchers Wang Min and Li Zhiheng from the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences (Institute of Paleontology, Chinese Academy of Sciences). The professional academic journal "Nature Ecology & Evolution" (Nature Ecology & Evolution) was published online.

　　The research team of the Institute of Paleontology of the Chinese Academy of Sciences said that the Late Mesozoic (170 million to 66 million years ago) recorded how birds evolved from dinosaurs and evolved unique body characteristics.

The diversity of bird lineages at this evolutionary stage is dominated by ornithoraxes composed of anti-birds and modern bird-types, and ornithoraxes have evolved a large number of morphological features similar to living birds, which are similar to the most primitive Birds (Archaeopteryx) vary enormously in morphology.

Non-bird-breasted birds (i.e., basal birds) whose evolutionary position is between the two have provided important information for filling this gap. different research.

　　The newly discovered Zhushi craton bird of prey is almost the same as theropod dinosaurs in terms of skull morphology, especially retaining the structure of the original archosaur double temporal foramen - the upper and lower temporal foramen are independent of the eye sockets and separated from each other. The pterygium has enlarged quadrate branches, and the vomer is thick.

These primitive features suggest that cratonic birds of prey did not evolve the skull mobility that most birds have, that is, the upper jaw moves independently of the cranium and lower jaw.

In contrast, the bones behind the head of the Zhu's craton already have the progressive features of a large number of birds, such as ossified sternum, elongated forelimbs, shortened coccyx, and opposite-handed claws, etc., indicating that its skull and body modules The evolution of the skull, especially the temporal and palatal regions, is relatively conservative in evolution.

The evolutionary track of the first metatarsal during dinosaur-bird evolution.

Photo courtesy of Wang Min

　　The research team pointed out that the most special feature of the Zhushi craton bird is its unusually long scapula and first metatarsal bone (equivalent to the innermost bone of the sole of the foot). Among them, the scapula is an important part of the bird's flight structure, and its shape varies in different flight Ways vary significantly among birds.

By comparing the cladistic method, they traced the dynamic trajectory of the two bones during the dinosaur-bird evolution and found that the length of the scapula was more likely to change in theropod dinosaurs than in birds. The independent lengthening in birds of prey may have been an attempt to adapt to flight, as the elongated scapula expanded the attachment area of ​​the muscles that control the downward flapping of the wings.

　　In addition, the relative length of the first metatarsal bone of the Zhushi craton bird is much longer than that of other birds and most dinosaurs.

In dinosaur-bird evolution, the first metatarsal bone showed a shortening trend. For example, the relative length ratio of the first metatarsal bone in birds was much smaller than that of the original theropod dinosaurs, while the proportion of the first metatarsal bone in birds was in its It has been established from the beginning.

　　The research team believes that the elongation of the first metatarsal in the Zhushi craton is the result of independent evolution. This conclusion can also be confirmed from the changes in the phylogenetic signal of the first metatarsal: the degree of its influence by the phylogenetic relationship is in Higher in theropods, but lower near parabirds.

Using ecological axis analysis, combined with the large first toe and curved claw, the research team proposed that the abnormal growth of the first metatarsal bone may be related to the raptor-like ecological habits of the Zhushi craton.

Restoration map of Zhu's craton bird of prey.

Photographed by Zhao Chuang

　　The team concluded that the unique scapula and metatarsal bones of the Zhushi craton bird show that under the dynamic action of individual development, natural selection and ecological function opportunities, some seemingly relatively conservative bones "get rid of the constraints" and undergo evolutionary changes Phenomenon.

　　It is understood that the newly discovered bird with a dinosaur skull and a weird body is named Zhushi Craton's bird of prey. Among them, "prey" means a ferocious bird, which is taken from Qu Yuan's "Li Sao" "The birds of prey are not flocking, Of course from the previous life"; the genus name "craton" was taken from the project "Craton destruction and terrestrial biological evolution" of the Basic Science Center of the National Natural Science Foundation of China; the species name was dedicated to the academician of the Chinese Academy of Sciences and geophysicist Zhu Rixiang, whose team was in North China A large number of important studies have been carried out on the mechanism of craton destruction.

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