Chinanews.com, Beijing, February 22 (Reporter Sun Zifa) The only known flying vertebrates on the earth are pterosaurs, birds and bats. Among them, the only extinct pterosaur is the earliest reptile that evolved powered flight Animals that conquered the blue skies some 70 million years before birds.
How did pterosaurs achieve flight?
What are the similarities and differences between its flight mechanism and that of birds and bats?
The researchers showed the Hami pterosaur shoulder belt fossil specimens studied in this study.
Photo by China News Agency reporter Sun Zifa
The research team of Wang Xiaolin and Zhou Zhonghe from the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences (Institute of Paleontology, Chinese Academy of Sciences) collaborated with the University of Chinese Academy of Sciences and the School of Ecology of Sun Yat-sen University, through the analysis of the early Cretaceous (about 130 million years ago) Hami in Xinjiang, China. The latest research on the morphology and bone histology of pterosaur fossil shoulder straps found that the flight mechanism of pterosaurs has both similarities with birds and bats and its own unique adaptations.
This important research paper revealing the flight mechanism of pterosaurs was recently published online in the international professional academic journal "The Anatomical Record" (The Anatomical Record) China Paleontology Special.
Dr. Wu Qian from the Institute of Paleospine of the Chinese Academy of Sciences introduced the results of this research.
Photo by China News Agency reporter Sun Zifa
What are the similarities to birds?
The co-first author of the paper, Dr. Wu Qian from the Institute of Paleospine of the Chinese Academy of Sciences, said that the membranous wings of pterosaurs made some early scholars think that their flight was similar to bats, but as research revealed that pterosaurs and birds have a closer phylogenetic relationship, Later scholars used birds more as reference objects for pterosaur flight research.
The research team's research on the Hami pterosaur shoulder belt bone fossils in the stratum about 130 million years ago in Hami, Xinjiang found that the flight mechanisms of the two are similar in two aspects:
Wu Qian, a doctor of the Institute of Paleospine, Chinese Academy of Sciences, presented and introduced the fossil specimens of Hami pterosaur shoulder girdle.
Photo by China News Agency reporter Sun Zifa
First, in terms of morphological research, computerized tomography (CT) 3D model reconstruction and morphological analysis of Hami pterosaur shoulder straps show that the supracoracoid muscle of pterosaurs, like birds, goes around the medial side of the coracoid process and connects to the proximal humerus , the coracoid process of the top crow can achieve a similar pulley function, and pterosaurs may use the contraction of the supracoracoid muscle to achieve wing lift just like birds.
Second, the histological study of the shoulder socket of pterosaurs found that cartilage tissue was suspected to be preserved in this position, indicating that the shoulder socket of pterosaurs may have thick articular cartilage like birds to buffer flight pressure.
Histological characteristics of the shoulder girdle of Pterosaur Hami.
Photo provided by Institute of Paleontology, Chinese Academy of Sciences
How does the unique flight mechanism behave?
Chen He, co-first author of the paper and a postdoctoral fellow at the School of Ecology of Sun Yat-sen University, pointed out that pterosaurs lacked a wishbone, scapula and dorsal vertebrae to form joints, and had features such as a healed scapula and black coracoid, which were obviously different from birds.
Its scapula and black coracoid fully healed before the individual became an adult, which represents a unique shoulder girdle adaptation during the evolution of pterosaur flight, and also shows that pterosaurs did not have a separate shoulder blade with the evolution of flight like birds- Coracoid joint.
Shoulder girdle specimens preserved with fossils such as Hami pterosaur skulls.
Photo provided by Institute of Paleontology, Chinese Academy of Sciences
Both the acetabular socket and the humeral head of pterosaurs present depressed articular surfaces, which may limit the rotation of the humeral head in the socket, suggesting that pterosaurs may control the rotation of the forearm through other special mechanisms to change the shape of the wing surface in flight.
As for the specific impact of these unique adaptations of pterosaurs on flight, the research team believes that further research is yet to be revealed.
Comparison of the morphology of the black coracoid of Hami pterosaur scapula and the shoulder girdle of birds, and the reconstruction of the shoulder joint and supracoracoid muscle.
Photo provided by Institute of Paleontology, Chinese Academy of Sciences
What is the direction of future research?
Corresponding author of the paper, researcher Wang Xiaolin, who has led the scientific expedition team to carry out field investigations and research work on Hami pterosaurs and their sedimentary strata in the past 20 years, said that it is generally believed that pterosaurs have strong flying capabilities, such as gliding, flapping and flying. Soaring can be used in all three flight modes, but the similarities and differences with birds and bats and the specific flight mechanism have not been very clear before.
He said that this research is the result of the cooperation between the pterosaurs and birds of the Institute of Paleontology of the Chinese Academy of Sciences, which mainly study flying vertebrates. It was found that the flight mechanism of pterosaurs is relatively complex, with both similarities to birds and bats, as well as its own unique adaptations. There is still huge room and potential for future research.
Jiang Shunxing, one of the authors of the paper and an associate researcher at the Institute of Paleospine of the Chinese Academy of Sciences, pointed out that the focus of this research is on the comparative analysis of the flight mechanisms of pterosaurs and birds, and less about the similarities and differences with bats.
Because both pterosaurs and bats use their bones to drive the skin to achieve flight, and the wings of the skin cannot create gaps like flying feathers. Therefore, pterosaurs need other methods to adjust the shape of their wings to reduce flight resistance. The next step is to focus on This question takes an in-depth study of the bat girdle, which also has skinned wings, to find the answer.
(over)