Fitting unanchored puzzle pieces in the skeleton: appropriate 3D scapular positions for the quadrupedal support in tetrapods
Fitting unanchored puzzle pieces in the skeleton: appropriate 3D scapular positions for the quadrupedal support in tetrapods
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DOI：
10.1111/joa.12778
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发表时间：
2018-05-01
影响因子：
2.4
通讯作者：
Fujiwara, Shin-ichi
中科院分区：
文献类型：
--
作者：
Fujiwara, Shin-ichi
推断已灭绝的四足动物骨骼的肩胛位置仍然很困难，因为肩胛骨和胸腔不是直接通过骨骼关节，而是通过胸肌相互连接。在现存的非睾丸四足四足动物中，肩胛骨/肩胛骨的顶部位置出现在胸腔的前部，脊柱上方并靠近正中面。使用 Felis、Rattus 和 Chamaeleo 的三维机械模型测试了该位置的充分性，这些模型假设单侧前肢和后肢的姿势。重力和反重力胸肌的收缩力产生的围绕髋臼的净力矩，以及肋骨对向下重力和反重力胸肌向上提升力之间的垂直压缩的抵抗力取决于肩胛骨的位置。四足动物常见的肩胛位置对应于身体抬起部分的滚转和偏航力矩可以忽略不计的位置，其中俯仰力矩足够大以抬起身体，并且位于具有高抗垂直压缩强度的肋骨上方。肩胛位置和胸腔形态之间的这些关系应该能够可靠地重建灭绝类群的肢体姿势。
Deducing the scapular positions of extinct tetrapod skeletons remains difficult, because the scapulae and rib cage are connected with each other not directly by skeletal joint, but by thoracic muscles. In extant non-testudine quadrupedal tetrapods, the top positions of the scapulae/suprascapulae occur at the anterior portion of the rib cage, above the vertebral column and near the median plane. The adequacy of this position was tested using three-dimensional mechanical models of Felis, Rattus and Chamaeleo that assumed stances on a forelimb on a single side and the hindlimbs. The net moment about the acetabulum generated by the gravity force and the contractive forces of the anti-gravity thoracic muscles, and the resistance of the rib to vertical compression between the downward gravity and upward lifting force from the anti-gravity thoracic muscle depend on the scapular position. The scapular position common among quadrupeds corresponds to the place at which the roll and yaw moments of the uplifted portion of the body are negligible, where the pitch moment is large enough to lift the body, and above the ribs having high strength against vertical compression. These relationships between scapular position and rib cage morphology should allow reliable reconstruction of limb postures of extinct taxa.