Senter Phil, Robins James H
Department of Biological Sciences, Fayetteville State University, Fayetteville, North Carolina, United States of America.
Department of Biology, Southeast Missouri State University, One University Plaza, Cape Girardeau, Missouri, 63701, United States of America.
PLoS One. 2015 Dec 16;10(12):e0144036. doi: 10.1371/journal.pone.0144036. eCollection 2015.
The inclination of the scapular blade and the resting pose of the forelimb in dinosaurs differ among reconstructions and among skeletal mounts. For most dinosaurian taxa, no attempt has previously been made to quantify the correct resting positions of these elements. Here, we used data from skeletons preserved in articulation to quantify the resting orientations of the scapula and forelimb in dinosaurs. Specimens were included in the study only if they were preserved lying on their sides; for each specimen the angle between forelimb bones at a given joint was included in the analysis only if the joint was preserved in articulation. Using correlation analyses of the angles between the long axis of the sacrum, the first dorsal centrum, and the scapular blade in theropods and Eoraptor, we found that vertebral hyperextension does not influence scapular orientation in saurischians. Among examined taxa, the long axis of the scapular blade was found to be most horizontal in bipedal saurischians, most vertical in basal ornithopods, and intermediate in hadrosauroids. We found that in bipedal dinosaurs other than theropods with semilunate carpals, the resting orientation of the elbow is close to a right angle and the resting orientation of the wrist is such that the hand exhibits only slight ulnar deviation from the antebrachium. In theropods with semilunate carpals the elbow and wrist are more flexed at rest, with the elbow at a strongly acute angle and with the wrist approximately at a right angle. The results of our study have important implications for correct orientations of bones in reconstructions and skeletal mounts. Here, we provide recommendations on bone orientations based on our results.
在恐龙的重建模型和骨骼标本中，肩胛骨的倾斜度以及前肢的静止姿势各不相同。对于大多数恐龙类群，此前尚未有人尝试对这些部位的正确静止位置进行量化。在此，我们利用关节相连保存的骨骼数据来量化恐龙肩胛骨和前肢的静止方位。仅当标本以侧卧姿势保存时才纳入研究；对于每个标本，仅当特定关节的关节结构得以保存时，该关节处前肢骨骼之间的角度才纳入分析。通过对兽脚亚目恐龙和始盗龙中骶骨长轴、第一背椎椎体与肩胛骨之间角度的相关性分析，我们发现椎体过度伸展对蜥臀目恐龙的肩胛骨方位并无影响。在所研究的类群中，肩胛骨长轴在双足蜥臀目恐龙中最为水平，在基干鸟脚亚目恐龙中最为垂直，而在鸭嘴龙超科恐龙中则处于中间状态。我们发现，在除具有半月形腕骨的兽脚亚目恐龙之外的双足恐龙中，肘部的静止方位接近直角，腕部的静止方位使得手部仅略微向尺侧偏离前臂。在具有半月形腕骨的兽脚亚目恐龙中，肘部和腕部在静止时更为弯曲，肘部呈强烈锐角，腕部近似直角。我们的研究结果对于重建模型和骨骼标本中骨骼的正确方位具有重要意义。在此，我们根据研究结果提供了关于骨骼方位的建议。
