Wu Qian, Chen He, Li Zhiheng, Jiang Shunxing, Wang Xiaolin, Zhou Zhonghe
University of the Chinese Academy of Sciences, Beijing, China.
Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China.
Anat Rec (Hoboken). 2023 Feb 14. doi: 10.1002/ar.25167.
As one of the mysteries volant vertebrates, pterosaurs were completely extinct in the K-Pg extinction event, which hampered our understanding of their flight. Recent studies on pterosaur flight usually use birds as analogies, since their shoulder girdle share many features. However, it was also proposed that these two groups may differ in some critical flight mechanisms, such as the primary muscles for the upstroke of the wings. Here, we describe and characterize the detail features of the pectoral girdle morphology and histology in Hamipterus from the Early Cretaceous of Northwest China for the first time. Our research reveals that the scapula and coracoid of Hamipterus form a synostosis joint, representing a distinct pectoral girdle adaption during pterosaur flight evolution, different from that of birds. The residual of the articular cartilage of the glenoid fossa supports the potential for cartilage tissue preservation in this location. The morphology of the acrocoracoid process of Hamipterus indicates it may work as a pulley for M. supracoracoideus as the main power of flight upstroke resembles that of birds. But the saddle type of the shoulder joint of the pterosaur may limit the rotation of the humerus head, suggesting a particular mechanism to control the angle of attack unlike birds. The presence of both the similarity and differences between the flight apparatus of pterosaurs and birds are highlighted in our research, which may be related to the flight mechanism and forelimb functional adaption. The distinctive feature of the flight apparatus of pterosaur should be treated with caution in future research, to better understand the life of this unique extinct volant vertebrate.
作为会飞的脊椎动物的谜团之一，翼龙在白垩纪-古近纪灭绝事件中完全灭绝，这阻碍了我们对其飞行的理解。最近关于翼龙飞行的研究通常以鸟类作类比，因为它们的肩带具有许多共同特征。然而，也有人提出这两类动物在一些关键飞行机制上可能存在差异，比如翅膀上抬的主要肌肉。在此，我们首次描述并刻画了来自中国西北早白垩世的哈密翼龙肩带形态学和组织学的详细特征。我们的研究表明，哈密翼龙的肩胛骨和乌喙骨形成了愈合关节，这代表了翼龙飞行演化过程中一种独特的肩带适应性，与鸟类不同。关节盂关节软骨的残留支持了该部位存在软骨组织保存的可能性。哈密翼龙乌喙骨突的形态表明，它可能起到了上喙肌滑轮的作用，因为飞行上抬的主要动力与鸟类相似。但翼龙肩关节的鞍型结构可能会限制肱骨头的旋转，这表明其控制迎角的机制与鸟类不同。我们的研究突出了翼龙和鸟类飞行器官的异同，这可能与飞行机制和前肢功能适应性有关。在未来的研究中，应谨慎对待翼龙飞行器官的独特特征，以便更好地了解这种独特的已灭绝会飞脊椎动物的生活习性。
